Washington ? As the Supreme Court was weighing a landmark gay rights case last year, Justice Antonin Scalia gave a keynote dinner speech in Philadelphia for an advocacy group waging a legal battle against gay rights.

Scalia addressed the $150-a-plate dinner sponsored by the Urban Family Council two months after hearing oral arguments in a challenge to a Texas law that made sex between gays a crime. A month after the dinner, he sharply dissented from the high court’s decision overturning the Texas law.

Some experts on legal ethics said they saw no problem in Scalia’s appearance before the group. But others say he should not have accepted the invitation because it called into question his impartiality on an issue that looms increasingly large on the nation’s legal agenda.

Scalia declined to comment on his appearance before the group.

Scalia’s activities outside the court in two other instances, one involving a hunting trip with a Kansas University dean, have also drawn criticism for suggesting partiality on cases before his court. But the Philadelphia dinner May 20, unlike the other cases, shows him appearing to support partisan advocates on a hotly disputed issue.

The Urban Family Council was not a party to the Texas case. But it is backing a separate lawsuit that seeks to overturn a Philadelphia city ordinance allowing gay couples who work for the city to register as “life partners” to qualify for pension and health benefits, which is an increasingly common practice.

William Devlin, who founded the council, is lead plaintiff in the lawsuit, which is pending before the Pennsylvania Supreme Court. Both sides say the case has a good chance of reaching Scalia’s court.

Supreme Court justices often speak to legal groups, such as bar associations and law school audiences. Some also have also spoken in recent years to legal groups with an ideological bent, such as the conservative Federalist Society or the liberal American Constitution Society.

But generally, they avoid any connection with or appearances before partisan or activist groups that fight for those issues in court.

The Philadelphia dinner marks the third instance in which Scalia’s outside activities have created an appearance of partiality on issues before the court.

The Los Angeles Times reported that Scalia flew in January on Air Force Two with Vice President Dick Cheney to go duck hunting in Louisiana, shortly after the high court decided to hear a legal challenge to Cheney’s intent to keep information secret about his energy policy task force.

The Times also found that in November 2001, Scalia was the guest speaker at Kansas University’s Law School at a time when the school’s dean was spearheading two cases before the court.