delivered the opinion of^ej3©trr-tr''
Appellants, approximately 64 in number, are members of the faculty, staff and student body of the University of Washington who brought this class action asking for a judgment declaring unconstitutional two Washington statutes requiring the execution of two different oaths by state employees and for an injunction against the enforcement of these statutes by appellees, the President of the University, members of the Washington State Board of Regents and the State Attorney General.
The statutes under attack are Chapter 377, Laws of 1955, and Chapter 103, Laws of 1931, both of which require employees of the State of Washington to take the oaths prescribed in the statutes as a condition of their employment. The 1931 legislation applies only to teachers, who, upon applying for a license to teach or renewing an existing contract, are required to subscribe to the following:
“I solemnly swear (or affirm) that I will support the constitution and laws of the United States of *494America and of the State of Washington, and will by precept and example promote respect for the flag and the institutions of the United States of America and the State of Washington, reverence for law and order and undivided allegiance to the government of the United States.” Wash. Laws 1931, c. 103.
The oath requirements of the 1955 Act, Wash. Laws 1955, c. 377, applicable to all state employees, incorporate various provisions of the Washington Subversive Activities Act of 1951, which provides generally that “[n]o subversive person, as defined in this act, shall be eligible for employment in, or appointment to any office, or any position of trust or profit in the government, or in the administration of the business, of this state, or of any county, municipality, or other political subdivision of this state.” Wash. Rev. Code § 9.81.060. The term “subversive person” is defined as follows:
“ ‘Subversive person’ means any person who commits, attempts to commit, or aids in the commission, or advocates, abets, advises or teaches by any means any person to commit, attempt to commit, or aid in the commission of any act intended to overthrow, destroy or alter, or to assist in the overthrow, destruction or alteration of, the constitutional form of the government of the United States, or of the state of Washington, or any political subdivision of either of them by revolution, force, or violence; or who with knowledge that the organization is an organization as described in subsections (2) and (3) hereof, becomes or remains a member of a subversive organization or a foreign subversive organization.” Wash. Rev. Code § 9.81.010 (5).
The Act goes on to define at similar length and in similar terms “subversive organization” and “foreign subversive organization” and to declare the Communist Party a sub*495versive organization and membership therein a subversive activity.1
On May 28, 1962, some four months after this Court’s dismissal of the appeal irf Nostrand v. Little, 368 U. S. 436, also a challenge to the 1955 oath,2 the University *496President, acting pursuant to directions of the Board of Regents, issued a memorandum to all University employees notifying them that they would be required to take an oath. Oath Form A3 requires all teaching per*497sonnel to swear to the oath of allegiance set out above, to aver that they have read, are familiar with and understand the provisions defining “subversive person” in the Subversive Activities Act of 1951 and to disclaim being a subversive person and membership in the Communist Party or any other subversive or foreign subversive organization. Oath Form B4 requires other state employees to subscribe to all of the above provisions except the 1931 oath. Both forms provide that the oath and *498statements pertinent thereto are made subject to the penalties of perjury.
Pursuant, to 28 U. S. C. §§ 2281, 2284, a three-judge District Courfi-was convened and a trial was had. That court determined that the 1955 oath and underlying statutory provisions did not infringe upon any First and Fourteenth Amendment'freedoms and. .were not unduly vague. In respect to the claim that the 1931 oath was unconstitutionally vague on its face,'the court held that although the challenge raised a substantial constitutional issue, adjudication was not proper in the absence of proceedings in the state courts which might resolve or avoid the constitutional issue. The action was dismissed. 215 F. Supp. 439. We noted probable jurisdiction because of-the public importance of this type of legislation and the recurring serious constitutional questions which it presents. 375 U. S. 808. We reverse.
I.
Appellants contend in this Court that the oath requirements and the statutory provisions on which they are based are invalid on their face because their language is unduly vague, uncertain and broad. We agree with this contention and therefore, without reaching the numerous other contentions pressed upon us, confine our considerations to that particular question.5
In Cramp v. Board of Public Instruction, 368 U. S. 278, the Court invalidated an oath requiring teachers and other employees of the State to swear that they had never lent their “aid, support, advice, counsel or influence to the Communist Party” because the oath was lacking in *499“terms susceptible of objective measurement” and failed to inform as to what the State commanded or forbade. The statute therefore fell within the compass of those decisions of the Court holding that a law forbidding or requiring conduct in terms so vague that men of common intelligence must necessarily guess at its meaning and differ as to its application violates due process of law. Connally v. General Construction Co., 269 U. S. 385; Lanzetta v. New Jersey, 306 U. S. 451; Joseph Burstyn, Inc., v. Wilson, 343 U. S. 495; United States v. Cardiff, 344 U. S. 174; Champlin Refining Co. v. Corporation Comm’n of Oklahoma, 286 U. S. 210.
The oath required by the 1955 statute suffers from similar infirmities. A teacher must swear that he is not a subversive person: that he is not one who commits an act or who advises, teaches, abets or advocates by any means another person to commit or aid in the commission of any act intended to overthrow or alter, or to assist the overthrow or alteration, of the constitutional form of government by revolution, force or violence. A subversive organization is defined as one which engages in or assists activities intended to alter or overthrow the Government by force or violence or which has as a purpose the commission of such acts. The Communist Party is declared in the statute to be a subversive organization, that is, it is presumed that the Party does and will engage in activities intended to overthrow the Government.6 Persons required to swear they under*500stand this oath may quite reasonably conclude that any person who aids the Communist Party or teaches or advises known members of the Party is a subversive person because such teaching or advice may now or at some future date aid the activities of the Party. Teaching and advising are clearly acts, and one cannot confidently assert that his counsel, aid, influence or support which adds to the resources, rights and knowledge of the Communist Party or its members does not aid the Party in its activities, activities which the statute tells us are all in furtherance of the stated purpose of overthrowing the Government by revolution, force, or violence. The questions put by the Court in Cramp may with equal force be asked here. Does the statute reach endorsement or support for Communist candidates for office? Does it reach a lawyer who represents the Communist Party or its members or a journalist who defends constitutional rights of the Communist Party or its members or anyone who supports any cause which is likewise supported by Communists or .the Communist Party? The susceptibility of the statutory language to require forswearing of an undefined variety of “guiltless knowing behavior” is what the Court condemned in Cramp. This statute, like the one at issue in Cramp, is unconstitutionally vague.7
*501The Washington statute suffers from additional difficulties on vagueness grounds. A person is subversive not only if he himself commits the specified acts but if he abets or advises another in aiding a third person to commit an act which will assist yet a fourth person in the overthrow or alteration of constitutional government. The Washington Supreme Court has said that knowledge is to be read into every provision and we accept this construction. Nostrand v. Balmer, 53 Wash. 2d 460, 483-484, 335 P. 2d 10, 24; Nostrand v. Little, 58 Wash. 2d 111, 123-124, 361 P. 2d 551, 559. But what is it that the Washington professor must "know”? Must he know that his aid or teaching will be used by another and that the person aided has the requisite guilty intent or is it sufficient that he know that his aid or teaching would or might be useful to others in the commission of acts intended to overthrow the Government? Is it subversive activity, for example, to attend and participate in international conventions of mathematicians and exchange views with scholars from Communist countries? What about the editor of a scholarly journal who analyzes and criticizes the manuscripts of Communist scholars submitted for publication? Is selecting outstanding scholars from Communist countries as visiting professors and advising, teaching, or consulting with them at the University of Washington a subversive activity if such scholars are known to be Communists, or regardless of their affiliations, regularly teach students *502who are members of the Communist Party, which by statutory definition is subversive and dedicated to the overthrow of the Government?
The Washington oath goes beyond overthrow or alteration by force or violence. It extends to alteration by “revolution” which, unless wholly redundant and its ordinary meaning distorted, includes any rapid or fundamental change. Would, therefore, any organization or any person supporting, advocating or teaching peaceful but far-reaching constitutional amendments be engaged in subversive, activity? Could one support the repeal of the Twenty-second Amendment or participation by this country in a world government? 8
*503II.
We also conclude that the 1931 oath offends due process because of vagueness. The oath exacts a promise that the affiant will, by precept and example, promote respect for the flag and the institutions of the United States and the State of Washington. The range of activities which are or might be deemed inconsistent with the required promise is very wide indeed. The teacher who refused to salute the flag or advocated refusal because of religious beliefs might well be accused of breaching his promise. Cf. West Virginia State Board of Education v. Barnette, 319 U. S. 624. Even criticism of the design or color scheme of the state flag or unfavorable comparison of it with that of a sister State or foreign country could be deemed disrespectful and therefore violative of the oath. And what are “institutions” for the purposes of this oath? Is it every “practice, law, custom, etc., which is a material and persistent element in the life or culture of an organized social group” or every “established society or corporation,” every “establishment, especially] one of a public character”?9 The oath may prevent a professor from criticizing his state judicial system or the Supreme Court or the institution of judicial review. Or it might be deemed to proscribe advocating the abolition, for example, of the Civil Rights Commission, the House Committee on Un-American Activities, or foreign aid.
It is likewise difficult to ascertain what might be done without transgressing the promise to “promote . . . undivided allegiance to the government of the United States.” It would not be unreasonable for the serious-minded oathtaker to conclude that he should dispense with lectures voicing far-reaching criticism of any old or new policy followed by the Government of the United *504States. He could find it questionable under this language to ally himself with any interest group dedicated to opposing any current public policy or law of the Federal Government, for if he did, he might well be accused of placing loyalty to the group above allegiance to the United States.
Indulging every presumption of a narrow construction of the provisions of the 1931 oath, consistent, however, with a proper respect for the English language, we cannot say that this oath provides an ascertainable standard of conduct or that it does not require more than a State may command under the guarantees of the First and Fourteenth Amendments.
As in Cramp v. Board of Public Instruction, “[t]he vice of unconstitutional vagueness is further aggravated where, as here, the statute in question operates to inhibit the exercise of individual freedoms affirmatively protected by the Constitution.” 368 U. S. 278, 287. We are dealing with indefinite statutes whose terms, even narrowly construed, abut upon sensitive areas of basic First Amendment freedoms. The uncertain meanings of the oaths require the oath-taker — teachers and public servants — to “steer far wider of the unlawful zone,” Speiser v. Randall, 357 U. S. 513, 526, than if the boundaries of the forbidden areas were clearly marked. Those with a conscientious regard for what they solemnly swear or affirm, sensitive to the perils posed by the oath’s indefinite language, avoid the risk of loss of employment, and perhaps profession, only by restricting their conduct to that which is unquestionably safe. Free speech may not be so inhibited.10 *505 Smith v. California, 361 U. S. 147; Stromberg v. California, 283 U. S. 359, 369. See also Herndon v. Lowry, 301 U. S. 242; Thornhill v. Alabama, 310 U. S. 88; and Winters v. New York, 333 U. S. 507.
1 — 1 h-[ h-i
The State labels as wholly fanciful the suggested possible coverage of the two oaths. It may well be correct, but the contention only emphasizes the difficulties with the two statutes; for if the oaths do not reach some or any of the behavior suggested, what specific conduct do the oaths cover? Where does fanciful possibility end and intended coverage begin?
It will not do to say that a prosecutor's sense of fairness and the Constitution would prevent a successful perjury prosecution for some of the activities seemingly embraced within the sweeping statutory definitions. The hazard of being prosecuted for knowing but guiltless behavior nevertheless remains. “It would be blinking reality not to acknowledge that there are some among us always ready to affix a Communist label upon those whose ideas they violently oppose. And experience teaches us that prosecutors too are human.” Cramp, supra, at 286-287. Well-intentioned prosecutors and judicial safeguards do not neutralize the vice of a vague law. Nor should we encourage the casual taking of oaths by upholding the discharge or exclusion from public employ*506ment of those with a conscientious and scrupulous regard for such undertakings.
It is further argued, however, that, notwithstanding the uncertainties of the 1931 oath and the statute on which it is based, the oath does not offend due process because the vagaries are contained in a promise of future conduct, the breach of which would not support a conviction for perjury. Without the criminal sanctions, it is said, one need not fear taking this oath, regardless of whether he understands it and can comply with its mandate, however understood. This contention ignores not only the effect of the oath on those who will not solemnly swear unless they can do so honestly and without prevarication and reservation, but also its effect on those who believe the written law means what it says. Oath Form A contains both oaths, and expressly requires that the signer “understand that this statement and oath are made subject to the penalties of perjury.” Moreover, Wash. Rev. Code §9.72.030 provides that “[e]very person who, whether orally or in writing . . . shall knowingly swear falsely concerning any matter whatsoever” commits perjury in the second degree. Even if it can be said that a conviction for falsely taking this oath would not be sustained, the possibility of a prosecution cannot be gainsaid. The State may not require one to choose between subscribing to an unduly vague and broad oath, thereby incurring the likelihood of prosecution, and conscientiously refusing to take the oath with the consequent loss of employment, and perhaps profession, particularly where “the free dissemination of ideas may be the loser.” Smith v. California, 361 U. S. 147, 151. “It is not the penalty itself that is invalid but the exaction of obedience to a rule or standard that is so vague and indefinite as to be really no rule or standard at all.” Champlin Refg. Co. v. Corporation Comm’n of Oklahoma, 286 U. S. 210, 243; cf. Small Co. v. American Refg. Co., 267 U. S. 233.
*507IV.
We are asked not to examine the 1931 oath statute because, although on the books for over three decades, it has never been interpreted by the Washington courts. The argument is that ever since Railroad Comm’n v. Pullman Co., 312 U. S. 496, the Court on many occasions has ordered abstention where state tribunals were thought to be more appropriate for resolution of complex or unsettled questions of local law. A. F. L. v. Watson, 327 U. S. 582; Spector Motor Service v. McLaughlin, 323 U. S. 101; Harrison v. NAACP, 360 U. S. 167. Because this Court ordinarily accepts the construction given a state statute in the local courts and also presumes that the statute will be construed in such a way as to avoid the constitutional question presented, Fox v. Washington, 236 U. S. 273; Poulos v. New Hampshire, 345 U. S. 395, an interpretation of the 1931 oath in the Washington courts in light of the vagueness attack may eliminate the necessity of deciding this issue.
We are not persuaded. The abstention doctrine is not an automatic rule applied whenever a federal court is faced with a doubtful issue of state law; it rather involves a discretionary exercise of a court’s equity powers. Ascertainment of whether there exist the “special circumstances,” Propper v. Clark, 337 U. S. 472, prerequisite to its application must be made on a case-by-case basis. Railroad Comm’n v. Pullman Co., 312 U. S. 496, 500; NAACP v. Bennett, 360 U. S. 471.11 Those special circumstances are not present here. We doubt, in the first place, that a construction of the oath provisions, in light of the vagueness challenge, would *508avoid or fundamentally alter the constitutional issue raised in this litigation. See Chicago v. Atchison, T. & S. F. R. Co., 357 U. S. 77. In the bulk of abstention cases in this Court,12 including those few cases where vagueness was at issue,13 the unsettled issue of state law principally *509concerned the applicability of the challenged statute to a certain person or a defined course of conduct, whose resolution in a particular manner would eliminate the constitutional issue and terminate the litigation. Here the *510uncertain issue of state law does not turn upon a choice between one or several alternative meanings of a state statute. The challenged oath is not open to one or a few interpretations, but to an indefinite number. There is no uncertainty that the oath applies to the appellants and the issue they raise is not whether the oath permits them to engage in certain definable activities. Rather their complaint is that they, about 64 in number, cannot understand the required promise, cannot define the range of activities in which they might engage in the future, and do not want to forswear doing all that is literally or arguably within the purview of the vague terms. In these circumstances it is difficult to see how an abstract construction of the challenged terms, such as precept, example, allegiance, institutions, and the like, in a declaratory judgment action could eliminate the vagueness from these terms. It is fictional to believe that anything less than extensive adjudications, under the impact of a variety of factual situations, would bring the oath within the bounds of permissible constitutional certainty. Abstention does not require this.
Other considerations also militate against abstention here. Construction of this oath in the state court, abstractly and without reference to concrete, particularized situations so necessary to bring into focus the impact of the terms on constitutionally protected rights of speech and association, Ashwander v. Tennessee Valley Authority, 297 U. S. 288, 341 (Brandeis, J., concurring), would not only hold little hope of eliminating the issue of vagueness but also would very likely pose other constitutional issues for decision, a result not serving the abstention-justifying end of avoiding constitutional adjudication.
We also cannot ignore that abstention operates to require piecemeal adjudication in many courts, England v. Louisiana State Board of Medical Examiners, 375 U. S. 411, thereby delaying ultimate adjudication on the merits *511for an undue length of time, England, supra; Spector, supra; Government & Civic Employees Organizing Committee v. Windsor, 353 U. S. 364,14 a result quite costly where the vagueness of a state statute may inhibit the exercise of First Amendment freedoms. Indeed the 1955 subversive person oath has been under continuous constitutional attack since at least 1957, Nostrand v. Balmer, 53 Wash. 2d 460, 463, 335 P. 2d 10, 12, and is now before this Court for the third time. Remitting these litigants to the state courts for a construction of the 1931 oath would further protract these proceedings, already pending for almost two years, with only the likelihood that the case, perhaps years later, will return to the three-judge District Court and perhaps this Court for a decision on the identical issue herein decided. See Chicago v. Atchison, T. & S. F. R. Co., 357 U. S. 77, 84; Public Utilities Comm’n of Ohio v. United Fuel Co., 317 U. S. 456.15 Meanwhile, where the vagueness of the statute deters constitutionally protected conduct, “the free dissemination of ideas may be the loser.” Smith v. California, 361 U. S. 147, 151.
V.
As in Cramp v. Board of Public Instruction, supra, we do not question the power of a State to take proper measures safeguarding the public service from disloyal con*512duct. But measures which purport to define disloyalty must allow public servants to know what is and is not disloyal. “The fact . . . that a person is not compelled to hold public office cannot possibly be an excuse for barring him from office by state-imposed criteria forbidden by the Constitution.” Torcaso v. Watkins, 367 U. S. 488, 495-496.
Reversed.