WHEN THE Reagan Administration argued in front of the Supreme Court this week for a narrow interpretation of Title IX of the Education Amendment Act of 1972, a law prohibiting sexual discrimination by any university receiving federal funds, it abandoned its passive disdain for women's rights in favor of an active hostility toward them.

Although we hope President Reagan stumbles over the gender gap in November, the recent decision is a dangerous precedent that threatens to outlive his tenure. Under the new ruling, universities may sexually discriminate so long as it is not in a program receiving any federal aid. This could lead to among other things, unequal treatment of women in hiring decisions, class selection, where limited, and athletics. Whereas previously Title IX insured the equal funding of both men's and women's sports, women's groups and civil liberties organizations are now predicting the revised law will lead to the demise of women's athletics. The ruling should hit women athletes especially hard in large universities that do not always share the Ivy League's commitment to women's sports, and spend larger sums for prominent men's programs such as football and basketball.

In the past, the threat of a termination in federal funds was government's most potent weapon with which to whip discriminatory institutions into line. Now, with all the teeth taken out of the ruling and the absence of an Equal Rights Amendment, women have virtually no recourse to legal protection during their years of education, having to rely instead, as one activist put it, "on good will rather than the law."

The ruling highlights not only the endangered status of women's equality, but also the growing conservatism of the Supreme Court. Having already appointed one justice, Reagan, if reelected, will have the opportunity to make as many as four appointments to the Court, insuring that his peculiar brand of conservatism will remain ensconced in federal judgement long after he returns to California.

Fortunately, the damage can be undone. Several Congressmen have already introduced legislation stipulating the termination of all federal funds to any university found sexually discriminating, and we urge Congress to move swiftly to pass the bill.

And voters should keep in mind that November's Presidential race will profoundly influence not only the Executive Branch, but the Judicial one as well.