(AP) — Justice Ruth Bader Ginsburg says the evolution of same-sex marriage reflects the genius of the U.S. Constitution.

The Supreme Court justice spoke steps from Independence Hall on Friday evening. She’s in Philadelphia for a discussion on her work on the court at the National Constitution Center.

Her remarks come just days after she performed the same-sex marriage of a friend in Washington, D.C.

Ginsberg Wedding

This photo provided by The Kennedy Center shows Michael M. Kaiser, left, and John Roberts, right, being married by Justice Ruth Bader Ginsberg, center, at the Kennedy Center on Saturday Aug. 31, 2013. (AP)

Ginsburg says equality has always been central to the Constitution, even if society has only applied it to women, blacks, gays and other minority groups over time.

Ginsburg is marking her 20th year on the court, and is now an outspoken voice of dissent on many high-profile cases.