
591 P.2d 241 (1979)
Stan DODD, Plaintiff and Appellant,
v.
The CITY OF EAST HELENA, a Montana Corporation, and John Verbanac, the Mayor of East Helena, Defendant and Respondent.
No. 14274.
Supreme Court of Montana.
Submitted on Briefs January 29, 1979.
Decided March 5, 1979.
Jackson & Kelley, Helena, for plaintiff and appellant.
Luxan, Murfitt, Davis & Cosgrove, Helena, for defendant and respondent.
Keller, Reynolds & Drake, Helena, for amicus curiae.
HARRISON, Justice.
This is an appeal by Stan Dodd, a former policeman in the City of East Helena, County of Lewis and Clark, Montana, from a ruling of the District Court of the First Judicial District, determining that he was not entitled to overtime compensation as a policeman of a third class city. The issue on appeal is whether or not the trial court properly determined that policemen of third class cities are not entitled to overtime compensation.
Appellant was employed as a policeman for the City of East Helena, Montana, from January 1, 1975, to May 19, 1977. Appellant has alleged that during this period he regularly worked overtime without any reimbursement. The City of East Helena admits that it did not pay any overtime to appellant during the period of his employment. The issue on appeal involves the sole question of whether or not policemen of third class cities are entitled to overtime compensation.
In 1971 the legislature enacted the Minimum Wages and Hours Act which was codified as section 41-2301, et seq., R.C.M. 1947, now section 39-3-401 et seq. MCA, which became effective July 1, 1971. In conformity with the provisions of the act, the Commissioner of Labor issued, on July 1, 1971, initial *242 regulations interpreting the provisions of the Minimum Wage Act. Request was made of the Commissioner by the Montana Police Association as to whether policemen were covered by the act and entitled to overtime compensation. The Commissioner by letter responded in the affirmative.
On July 27, 1971, a petition for a declaratory judgment was filed in this Court in Cause No. 12100, entitled the City of Billings and Yellowstone County v. The Honorable Sid Smith, Commissioner of Labor of the State of Montana. Numerous issues were raised in the petition regarding the validity and coverage of the Minimum Wage Act. The petition alleged (1) that the act was unconstitutional and void, and (2) that police officers, firemen, and deputy sheriffs were excluded from the provisions therein on the grounds that each was a professional. This Court accepted original jurisdiction and issued its opinion on October 29, 1971. City of Billings v. Smith (1971), 158 Mont. 197, 490 P.2d 221. The act was determined to be constitutional, but we held that policemen were bona fide professionals and thereby exempt from its provisions.
By reason of this Court's decision, the 1973 legislature amended the Municipal Police Act by enactment of section 11-1832.2, R.C.M. 1947, now section 7-32-4119 MCA, which provides:
"Members of the police departments of cities of the first and second class, except those officers holding the rank of captain or above, are entitled to compensation for overtime as provided under section 41-2303(b)."
The Billings determination by this Court was not limited in any way to the policemen working in cities of any specific size. On the contrary, for the reasons set forth in the opinion, they are applicable to policemen working in any city or town in the State of Montana. In fact, the legislative treatment of policemen referred to in the opinion is contained in what is known as the Municipal Police Act, section 11-1801, et seq., R.C.M. 1947, now section 7-32-4101 et seq. MCA, which provides the basic guidelines for all cities and towns for the administration and operation of their police departments.
As a result of the Billings decision, no policemen in Montana were entitled to receive any overtime compensation. As noted, the 1973 legislative assembly amended the Police Act by adding section 11-1832.2, R.C.M. 1947, now section 7-32-4119 MCA. According to the amendment, those policemen in first and second class cities became entitled to overtime compensation. The decision in Billings applied to all policemen. The effect of section 11-1832.2 was that the legislature overruled the Billings decision only as it applied to policemen in first and second class cities. Consequently, policemen employed by cities of the third class were not entitled to receive overtime compensation.
The decision of this Court has not been changed by the legislature or by this Court. All the arguments of appellant notwithstanding, the state of the law at this time is that while the Billings decision applied to all policemen, there is a special act which now segregates third class city policemen.
Subissue (a) set forth by appellant is whether the Billings decision contains an inherent conflict which must be addressed by this Court. Appellant argues that there is conflict in the reasoning of this Court's opinion which must be clarified. He argues that "[I]f policemen are excluded from the Minimum Wages Act, then there can be no conflict between the Minimum Wage Act and Section 25-604. This inherent contradiction should be addressed and clarified by the Honorable Supreme Court of the State of Montana." The contradiction which appellant addresses does not exist.
The Billings case held that policemen were excluded from the terms of the act because of their separate treatment under the terms of the Municipal Police Act, Chapter 18, Title 11. The statute referred to by appellant, section 25-604, R.C.M. 1947, now sections 7-4-2505 and -2402 MCA, relates only to compensation for deputy sheriffs. This Court in finding that a deputy *243 sheriff was excluded referred to a conflict between the specific statute (25-604) specifying their pay and the general statute, the Minimum Wage Act, and a determination of which statute would govern. That discussion had nothing to do with the rationale for finding that policemen were professionals. We find no conflict in the opinion which requires further clarification.
Appellant next addresses his subissue (b) concerning the effect of the legislature's enactment of section 11-1832.2, R.C.M. 1947, now section 7-32-4119 MCA. Appellant argues that the omission of policemen of third class cities from the statute was a mistake and that this Court should correct same. He states that "therefore, it is quite evident that the insertion of first and second class cities in the above act was either a drafting error or inserted simply through the ignorance of the possible consequences." The argument that this exclusion was "scrivener's error" on the part of the legislature and the request that this Court rewrite the statute to insert third class cities within its provisions contain no citation of authority to support such an action by this Court.
We have held on numerous occasions that this Court cannot rewrite statutes to omit what parties feel should be omitted or insert what parties feel should be inserted. In a recent decision, Mont. Depart. of Rev. v. Am. Smelting & Refining (1977), Mont., 567 P.2d 901, 905-06, 34 St.Rep. 597, 602, the Court said:
"The function of the Supreme Court when construing a statute is simply to ascertain and declare what is in substance stated therein, and not to insert what has been omitted or to omit what has been inserted. (Citations omitted.) The fundamental rule of statutory construction is that the intent of the legislature controls. (Citations omitted.) Where the intent of the legislature can be determined from the plain meaning of the words used, the courts may not go further and apply any other means of interpretation ..."
See also Matter of Estate of Baier (1977), Mont., 567 P.2d 943, 34 St.Rep. 860; Myers v. 4 B's Restaurant, Inc. (1977), 172 Mont. 159, 561 P.2d 1331, 34 St.Rep. 187; Lester v. J. & S. Investment Company (1976), 171 Mont. 149, 557 P.2d 299, 33 St.Rep. 1104; State ex rel. Nawd's T.V. & App. Inc. v. District Court (1975), 168 Mont. 456, 543 P.2d 1336.
Applying these rules of statutory construction supports the proposition that there is no mistake on the part of the legislature. It specifically mentioned cities of first and second class only and failed to mention cities of third class or towns. We are bound by the following rule of statutory construction: "... It is a rule of statutory construction that the express mention of one matter excludes other similar matters not mentioned ..." Helena Valley Irr. Dist. v. State Highway Comm'n (1967), 150 Mont. 192, 198, 433 P.2d 791, 794.
It was also noted in the above entitled case that there is a presumption that the legislature acts knowing full well the facts existing at the time of the enactment of the legislation. "It is also a rule of statutory construction that the legislature acted with full knowledge and information as to the subject matter and existing conditions including the construction placed on previous law by the executive officers acting under it ..." 150 Mont. at 199, 433 P.2d at 794.
The legislature obviously was aware of the Billings decision when it amended the act to include policemen of first and second class cities and knew full well of the effect of this act and intended specifically to limit it to the larger cities and to exclude the smaller cities.
Appellant argues that the enactment of section 11-1832.2 repealed the Billings decision. We do not agree. All that was done was to provide certain policemen with overtime compensation. The effect of the legislation did not affect the status of policemen in third class cities, and they are still bound by the provisions of the Billings decision. It is a legislative matter to decide whether or not policemen of third class cities and towns are to be given overtime compensation.
*244 Appellant then raises the issue of whether section 11-1832.2 violates the rights of policemen in third class cities by denying them overtime. This issue of unconstitutionality of the treatment of policemen of third class cities was raised for the first time on appeal. No attempt was made by appellant to serve the Attorney General of the State of Montana. We hold, therefore, that the issue is not properly before this Court.
This Court in Johnson v. Doran (1975), 167 Mont. 501, 511, 540 P.2d 306, 311, stated, "As to Doran's contention that section 66-1940(c), R.C.M. 1947, is unconstitutional, this issue was raised for the first time on appeal. This Court has consistently ruled that a constitutional issue is waived if not presented at the earliest opportunity . ." See also Clontz v. Clontz (1975), 166 Mont. 206, 531 P.2d 1003; Union Interchange, Inc. v. Allen (1962), 140 Mont. 227, 370 P.2d 492; Rule 38, M.R.App.Civ.P.
The decision of the District Court is affirmed.
HASWELL, C.J., and DALY, SHEA and SHEEHY, JJ., concur.
