Appellant challenges the constitutionality of 12 O.S.Supp.1979, § 1289(D)1 which makes the voluntary cohabitation of a former spouse with a member of the opposite sex a ground for reducing or terminating support alimony.
Parties were granted a divorce October 26, 1979, with appellee ordered to pay a total of $10,000.00 in support alimony in three payments: $2,000.00 at the time of the divorce decree, $3,000.00 on December 20, 1979 and $5,000.00 on or before March 26, 1980.
Appellee made the first payment on December 26,1979; he filed a motion to modify the divorce decree by terminating the other alimony payments. On March 26, 1980 the trial court granted appellee’s motion and terminated the final two alimony payments, one due before the filing of the motion and the other one due after the granting of the motion.
Appellant attacks the constitutionality of the statute as violative of equal protection and due process because (1) the statute does not allow a party the right to seek an increase in support alimony upon a showing of substantial change of condition and (2) the described cohabitation penalizes only the recipient of alimony, not the other spouse who also engages in such conduct. Appellant also alleges the trial court erred in finding a “substantial change of circumstances,” warranting termination of support alimony and also erred in finding that a “private conjugal relationship” existed.
Appellant cites only two cases as authority for her constitutional challenge. One case2 simply offers a definition of “alimony” which is of no help here. The second case3 offers wisdom from New York State that “even immoral conduct will not permit the court to make a modification unless the type of conduct engaged in is contemplated by the statutory language ... the power to modify a provision for alimony is only such as is conferred by statute .... ” We find such language is of little assistance to appellant in light of our statute.
The raison d’etre of § 1289(D) is not to regulate morality, but rather to regulate support maintenance when the need for continued support has diminished or vanished. Aside from voluntary cohabitation, there must be present, and proved, a “substantial change of circumstances relating to need for support or ability to support.”
A judgment in a divorce suit may only be modified or vacated under one of *155the statutory provisions enumerating situations wherein the trial court is granted such power, unless it is held to be a void judgment. Fisher v. Fisher, 558 P.2d 391 (Okla.1976). We have held that where alimony has been allowed to a wife in a divorce decree, the court has no power on subsequent application to increase or diminish the allowance given in the original judgment without statutory authority. Funnell v. Funnell, 584 P.2d 1319 (Okla.1978); Fisher v. Fisher, supra.
We find nothing unconstitutional in § 1289(D). To argue the giver of support alimony should be penalized for engaging in voluntary cohabitation is ludicrous; what possible bearing would that have on the need for support of the recipient spouse? Support alimony is a final judgment; it can be neither increased nor decreased absent specific statutory authority. We find nothing constitutionally infirm in a statute which provides for a decrease in support alimony, and as appellant can point us to no authority to support her argument, we dismiss it.
Appellant’s final propositions of error argue there was insufficient evidence to find “cohabitation,” “a private conjugal relationship” and “a substantial change in circumstances.”
The trial court spent considerable time examining the evidence and listening to the witnesses and absent an abuse of discretion this Court will not reverse a discretionary decision by a trial court based on the evidence. Walker v. Walker, 140 Okla. 1, 282 P. 361 (1929); Hughes v. Hughes, 363 P.2d 155 (Okla.1961).
AFFIRMED.
HODGES, LAVENDER and HAR-GRAVE, JJ., concur. BARNES, C.J., and OPALA, J., concur and file separate opinions. SIMMS, V.C.J., and IRWIN and WILSON, JJ., dissent..12 O.S.Supp.1979, § 1289(D): “The voluntary cohabitation of a former spouse with a member of the opposite sex shall be a ground to modify provisions of a final judgment or order for alimony as support. If voluntary cohabitation is alleged in a motion to modify the payment of support, the court shall have jurisdiction to reduce or terminate support payments upon proof of substantial change of circumstances relating to need for support or ability to support. As used herein, cohabitation shall mean the dwelling together continuously and habitually of a man and a woman who are in a private conjugal relationship not solemnized as a marriage according to law, or not necessarily meeting all the standards of a common-law marriage. The petitioner shall make application for modification and shall follow notification procedures as used in other divorce decree modification actions. The court that entered the divorce decree shall have jurisdiction over the modification application.”
. Poloke v. Poloke, 37 Okla. 70, 130 P. 535 (Okla.1913).
. Northrup v. Northrup, 43 N.Y.2d 566, 402 N.Y.S.2d 997, 373 N.E.2d 1221 (N.Y.1978).