Washington ? Stung by a Senate setback on gay marriage, Republicans passed legislation in the House Thursday to prevent federal courts from ordering states to recognize same-sex unions sanctioned elsewhere.

Democrats called the bill an unconstitutional attack on gays and the federal judiciary, and said its passage was just a matter of election-year politics.

A day before Congress closes down for six weeks, the 233-194, mainly party-line vote handed at least a symbolic victory to social conservatives who form a key Republican constituency. The bill has the strong backing of the Bush administration, but is not expected to make headway in the Senate, aides to Democrats and Republicans said.

Last week, the Senate failed to advance a constitutional amendment banning gay marriage.

Supporters said the House legislation would protect the institution of marriage by reining in federal judges who might otherwise impose gay marriage on states that have banned it. “Marriage is under attack,” said Rep. James Sensenbrenner, R-Wis., referring to the Massachusetts state court decision allowing same-sex marriages.

The bill would strip the Supreme Court and other federal courts of their jurisdiction to rule on challenges to state bans on gay marriages under a provision of the 1996 federal Defense of Marriage Act. That law defines marriage as between a man and a woman, and says states are not compelled to recognize gay marriages that take place in other states.

The nonpartisan Congressional Research Service said it could find no precedent for Congress passing a law to limit federal courts from ruling on the constitutionality of another law, although Democrats said opponents of civil rights legislation tried to do the same thing.

The effect of the bill would be to single out gays and lesbians, barring them from going into federal court to seek to have their marriages recognized, several Democrats said. Civil rights groups said the bill was unconstitutional for that reason.

“We face no less than a sign on the courthouse door: ‘You may not defend your constitutional rights in this court. You may not seek equal protection here,”‘ said Rep. Tammy Baldwin, D-Wis., the House’s lone declared lesbian. “Today, the ‘you’ is gay and lesbian citizens. But who would be next?”