President Obama made good on the promise of his second Inaugural Address on Thursday by joining the fight to overturn California’s ban on same-sex marriage. Since he declared that marriage equality is part of the road “through Seneca Falls and Selma and Stonewall,” we can’t imagine how he could have sat this one out.

The administration’s brief to the Supreme Court was a legally and symbolically important repudiation of Proposition 8, the 2008 voter referendum that amended California’s Constitution to forbid bestowing the title of marriage on a union between two people of the same sex — a right the California Supreme Court had found to be fundamental under the State Constitution.

Like the arguments made by the lawyers for those who seek to overturn Proposition 8, and by a group of prominent Republicans earlier this week, the government’s brief says any law attempting to ban same-sex marriage must be subjected to heightened scrutiny because it singles out a class of Americans, historically subject to discrimination, for unequal treatment.

The brief said California’s civil unions law provides the rights and protections of marriage, so Proposition 8’s denial of the designation of marriage “does not substantially further any important governmental interest.”