The Obama administration announced Thursday that it will formally support the Supreme Court challenge to Proposition 8, the 2008 referendum that banned same-sex marriage in California.

According to ABC News, at President Barack Obama’s urging, the Justice Department has announced that it will throw its support behind the effort to declare Proposition 8 unconstitutional. On Thursday, the department filed a friend-of-the-court brief in support of the two gay couples leading the case against Proposition 8.

In addition to the Justice Department’s support, 13 states have also filed briefs against Prop 8, according to the Huffington Post.

Prop 8, which was approved by 52 percent of California voters in 2008, outlawed same-sex marriage a few months after they began under a state court decision. The measure has been challenged in numerous courts, and has now worked its way up to the Supreme Court. In the brief window before Prop 8 passed, 18,000 same-sex couples were married in California.

Up until 2012, Obama stuck strictly to the sidelines on marriage equality, but in May of that year, he stated, after "evolving" on the issue, that “same-sex couples should be able to get married.”

Since then, Obama has been stepping up his rhetoric in a push to allow same-sex marriage, including in his second Inaugural Address. 

"Our journey is not complete until our gay brothers and sisters are treated like anyone else under the law, for if we are truly created equal, then surely the love we commit to one another must be equal as well,” the president declared on Jan. 21.

Along with the Proposition 8 case, the Supreme Court is also taking a up challenge to the constitutionality of the 1996 Defense of Marriage Act. DOMA is a federal ban on gay marriage which denies same-sex couples federal benefits. According to Salon, 15 states have filed briefs against DOMA as well.