State laws that require divorced husbands but not wives to pay alimony were held unconstitutional by the Supreme Court yesterday.

The obligation to pay alimony rests with the spouse able to pay it, whether man or woman, the court ruled 6 to 3.

The justices acted in a case from Alabama, one of 11 states with laws that prohibit a woman from paying alimony even if her former husband is in need and she isn't.

The other states are Georgia, Idaho, Louisiana, Mississippi, Nevada, New York, South Carolina, South Dakota, Tennessee and Wyoming.

The goal of such statutes, Justice William J. Brennan Jr. wrote for the court, was generally to compensate women "for past discrimination during marriage, which assertedly has left them unprepared to fend for themselves in the working world following divorce."

But, he said, they deny the equal protection of the laws guaranteed by the Constitution without a showing that such a denial is required to serve important government objectives.

"There is no reason... to use sex as a proxy for need," Brennan wrote. "Needy males could be helped along with needy females with little, if any, additional burden on the state."

Alabama's purported desire to compensate for and ameliorate the effects of past discrimination would be "as well-served by a gender-neutral classification as one that gender-classifies and therefore carries with it the baggage of sexual stereotypes," Brennan wrote. The state in these circumstances "cannot be permitted to classify on the basis of sex."

He said this is "doubly so" in a case such as the one decided yesterday, in which the Alabama laws appeared to redound -- if only indirectly -- to the benefit of a woman "without need for special solicitude."

The case arose from the divorce of William H. and Lillian M. Orr, a childless Auburn, Ala., couple, in February 1974.

The final decree required Orr, whose taxable income then was $26,000, to pay his former wife $1,240 a month ($14,880 a year), forfeit his interest in their home, pay her lawyers' fees of $3,500, let her keep a 1973 Chevrolet Corvette, and pay her lifeinsurance premiums on policies with a face value of $108,000. She now lives in Opelika.

By August 1976, Orr, now president of Orrox Corp. in Santa Clara, Calif., was in arrears. Under a motion by his former wife, a court judgment of $5,524 was entered against him. He challenged the constitutionality of the Alabama alimony laws because they impose the burden only on one sex, but he lost in the state courts.

In a dissenting opinion yesterday, Justice William H. Rehnquist, joined by Chief Justice Warren E. Burger, didn't side either with Brennan or Mrs. Orr on the equal-protection issue. Instead, he questioned William Orr's legal right to challenge the state laws, never having sought and being ineligible for alimony for himself, and having paid alimony to his former wife, without objection, for two years.

In a detailed rejection of Rehnquist's contention, Brennan transposed the issue to the sphere of race. "There is no doubt that a state law imposing alimony obligations on blacks but not whites could be challenged by a black who was required to pay," Brennan said. "The burden alone is sufficient to establish standing."

In the second dissent, Justice Lewis F. Powell Jr., agreeing with Rehnquist, raised the possibility that the Orrs weren't "fully adversarial" or that they weren't "seeking -- for reasons undisclosed -- a purely advisory opinion on a constitutional issue of considerable importance."

Brennan found it "surprising, indeed disturbing," that Powell should suggest that the Orrs "may have colluded... No evidence whatever, within or outside the record, supports that accusation. And our Brother Powell suggests none. Indeed, it is difficult to imagine what possible interest Mrs. Orr could have in helping her exhusband resist her demand for $5,524 in back alimony."