Plaintiff, Beadling, served as Director of the House of Representatives Fiscal Agency1 since 1970. On January 27, 1977, he was fired from that position by the House Appropriations Committee. Plaintiff is also a veteran of the United States Navy, having been honorably discharged from that service branch in November of 1954.
On February 7, 1977, plaintiff wrote to the Governor and requested a hearing concerning his discharge pursuant to the preference in employment act, MCL 35.401 et seq.; MSA 4.1221 et seq.2 *533Plaintiff received a response from the Governor one week later which indicated that appropriate action would be taken once an opinion from the Attorney General was received. Plaintiff waited for further reply and then commenced the present mandamus action on July 27, 1977. Following trial on a stipulated set of facts, the lower court denied mandamus relief. Plaintiff appeals as of right.
The issuance of a writ of mandamus is not a matter of right but is discretionary and is governed by equitable principles. Board of Education of Oakland Schools v Superintendent of Public Instruction, 401 Mich 37, 43-44; 257 NW2d 73 (1977).
"Mandamus lies only when there is a clear legal duty incumbent on the defendant and a clear legal right in the plaintiff to the discharge of such duty. Miller v Detroit, 250 Mich 633; 230 NW 936 (1930). The specific act sought to be compelled must be of a ministerial nature, that is, prescribed and defined by law with such precision and certainty as to leave nothing to the exercise of discretion or judgment. Taylor v Ottawa Circuit Judge, 343 Mich 440; 72 NW2d 146 (1955), Bills v Grand Blanc Twp, 59 Mich App 619; 229 NW2d 871 (1975), State Board of Education v Garden City School Dist, 62 Mich App 376; 233 NW2d 547 (1975).” Board of County Road Comm’rs of the County of Oakland v State Highway Comm, 79 Mich App 505, 509; 261 NW2d 329 (1977).
This Court will not interfere with the denial of mandamus relief absent a clear abuse of discretion. Cyrus v Calhoun County Sheriff, 85 Mich App 397, 399; 271 NW2d 249 (1978).
*534The lower court concluded that the Legislature did not intend to include itself within the provisions of the preference in employment act. This conclusion was reached through interpretation of the statutory authorization for the agency, MCL 4.326a; MSA 2.138(16a), and reliance on Board of Education of City of Detroit v Campbell, 256 Mich 350; 239 NW 370 (1931).
The Campbell decision concerned a bylaw adopted by the Detroit Board of Education requiring employees to retire at the age of 70. The defendant protested his mandatory retirement, alleging that it violated the act as applied to municipalities. The school board prevailed in a declaratory action, and the Supreme Court affirmed. The Court stated that school districts were not within the confines of the act since they were neither "public departments”, "public works”, nor "municipalities”. Further, it was observed that the statute creating school districts gave school boards full power over their teachers and other employees "notwithstanding any general or special law to the contrary”. The Court viewed that as evidence of a legislative intent to exclude school districts from the act. Id., 354-355.
The statute creating the House Fiscal Agency lacks similar language and, therefore, does not by its own terms exclude the agency from the ambit of the preference in employment act. Further, it appears that the act itself includes the Legislature within the definition of "public department”.
The primary rule of statutory construction is to determine and effectuate the Legislature’s intent. King v Director of Midland County Dep’t of Social Services, 73 Mich App 253, 258; 251 NW2d 270 (1977). The statute here was originally enacted as 1897 PA 205 and was designed to give preference *535to Civil War veterans seeking employment in public departments and public works. However, the right to a hearing prior to discharge was only provided to veterans employed in public works.3 Veterans working in public departments were provided the right to a hearing by a subsequent amendment to the act. 1907 PA 329.
The 1907 amendment was an apparent response to the narrow interpretation given to the act in Ellis v Common Council of Grand Rapids, 123 Mich 567, 569; 82 NW 244 (1900). In Ellis, the Supreme Court refused to extend the hearing right to veterans employed in public departments. The Court stated:
"A 'public department’ is defined as 'a division of official duties or functions; a branch of government; a distinct part of a governmental organization: as, the legislative, executive, and judicial departments; the department of state, of the treasury, etc.’ ”
At the time, the Michigan Constitution divided the *536government into three "departments”: the legislative, executive, and judicial. Const 1850, art 3, § 1.
The Legislature is presumed to be aware of judicial interpretation of a statute, and when the statute is substantially reenacted the Legislature is deemed to have adopted that construction. Jeruzal v Wayne County Drain Comm’r, 350 Mich 527, 534; 87 NW2d 122 (1957). Here, the Legislature can be presumed to have adopted the Ellis definition of public department and to have intended to include its own employees within the act.
Nevertheless, the act is unconstitutional when applied in this manner. Article 3, §2 of the 1963 Constitution provides:
"The powers of government are divided into three branches: legislative, executive and judicial. No person exercising powers of one branch shall exercise powers properly belonging to another branch except as expressly provided in this constitution.”
This section makes it clear that the three government branches are to be separate and coequal. In the Matter of the Petition for a Representation Election Among Supreme Court Staff Employees, 406 Mich 647, 662; 281 NW2d 299 (1979). The concept of separation of powers would be violated if the executive branch was allowed to judge the competency of a discharged employee of the legislative branch and order reinstatement. Plaintiffs position was one of some sensitivity within the legislative process. His responsibilities included review of the Governor’s proposed budgets and development of the Legislature’s proposed budgets. To permit executive overview of that position would allow a dangerous incursion into the legislative realm.
While the constitution expressly permits the *537Legislature to enact laws for the resolution of disputes involving public employees, Const 1963, art 4, §48,4 that provision is inapplicable in this situation since it would otherwise substantially impair the separation of powers clause. Cf., People v Blachura, 390 Mich 326, 333; 212 NW2d 182 (1973).
In summary, although the lower court erred in concluding that the Legislature intended to exclude itself from the preference in employment act, denial of mandamus relief was nonetheless appropriate as application of the statute to legislative employees is unconstitutional.
Affirmed.