The U.S. Supreme Court has handed down two landmark same-sex marriage rulings, one striking down a major provision of the federal Defense of Marriage Act (DOMA) and the other leaving uncertain the fate of California’s Proposition 8, the 2008 ballot initiative that prohibits gay and lesbian couples in the state from marrying.

Federal Defense of Marriage Act Unconstitutional

In the DOMA case, U.S. v. Windsor, a divided court ruled 5-4 that by denying legally wed same-sex couples marital status under federal law, DOMA overreaches into states’ legitimate authority to regulate marriage. Writing for the majority, Justice Anthony Kennedy points out that history and tradition have given the states the power to determine their own rules for marriage without significant federal interference. Kennedy goes on to say that by not recognizing same-sex marriages that have been legally performed in various states, DOMA “rejects the long established precept that the incidents, benefits, and obligations of marriage are uniform for all married couples within each state.”

In addition, the court ruled, DOMA violates the Fifth Amendment’s guarantee of “equal liberty.” Kennedy’s majority opinion states that DOMA “singles out” legally married same-sex couples and imposes a second-class status on them even though their own states have accorded them full marriage rights. Furthermore, Kennedy writes, DOMA advances no government policy or purpose that justifies its discriminatory impact. “The statute is invalid, for no legitimate purpose overcomes the purpose and effect to disparage and to injure those who the State, by its marriage laws, sought to protect in personhood and dignity.”

In 1996, Congress passed the Defense of Marriage Act with bipartisan support, and the bill was signed into law by then-President Bill Clinton. The law also gives states the right to refuse to recognize same-sex marriages legally performed in other jurisdictions. This provision was not at issue in U.S. v. Windsor and was not struck down.

The provision of DOMA that was ruled unconstitutional is Section 3, which states that the federal government does not recognize same-sex marriage for any purpose, including the filing of taxes or the distribution of federal benefits such as Social Security.

By striking down Section 3 of DOMA, the Supreme Court clears the way for married gay and lesbian couples living in states where same-sex marriage is legal to receive all the federal benefits currently available to married opposite-sex couples. Same-sex couples who are legally married but living in states that do not recognize same-sex marriage likely will receive only some federal benefits, such as veterans’ benefits. The ruling in Windsor does not go so far as to establish a constitutional right to same-sex marriage.

Uncertainty in the Wake of Proposition 8 Decision

The impact of the court’s ruling in its other same-sex marriage case, Hollingsworth v. Perry, is more complicated. In a 5-4 opinion written by Chief Justice John Roberts, the high court ruled that the private parties who were defending California’s Proposition 8 lacked standing under Article III of the Constitution. Standing is the legal concept that only those with a legitimate stake in a case’s outcome can be a party to a lawsuit. In this case, Proposition 8 was approved by California’s voters, but state officials refused to defend it in court, leaving an ad hoc group of the ballot initiative’s supporters to take up the mantle. As a result of its ruling that these supporters did not have standing, the court refused to decide the proposition’s constitutionality. Instead, the justices sent the case back to the 9th U.S. Circuit Court of Appeals, which had ruled the proposition was unconstitutional, with an order to vacate their opinion and dismiss the appeal.

Proposition 8, an amendment to the California constitution to ban same-sex marriage, was approved by California voters in November 2008. It was adopted in response to a ruling earlier that year by the state’s Supreme Court, which had determined that the state constitution gave same-sex couples in the Golden State full marriage rights. When voters approved Proposition 8, they nullified the state court’s decision. In a subsequent lawsuit, Proposition 8 was struck down as unconstitutional by a federal district court, a decision that was affirmed by the 9th Circuit Court.

The Supreme Court’s dismissal of the 9th Circuit’s ruling in Hollingsworth leaves the status of same-sex marriage in California in limbo. While the appeals court ruling has been vacated, the district court’s decision that Proposition 8 is unconstitutional remains intact. This means that, at the very least, the two same-sex couples who originally brought the suit against Proposition 8 in district court now will have the right to marry. But it is unclear whether the district court’s order gives marriage rights to any other couples, even in the district where this particular court has jurisdiction (the San Francisco Bay Area).

There likely will be legal action on multiple fronts attempting to clarify the status of same-sex marriage across California. This may include additional suits in federal district courts as well as in state courts. In addition, a referendum on whether to repeal Proposition 8 is likely to be on the ballot in California in November 2014.

Both of the Supreme Court decisions come in the wake of significant shifts in public opinion on same-sex marriage. As recently as 2008, the year Proposition 8 was approved by California voters, a majority of Americans (51%) opposed same-sex marriage. According to combined data from two 2013 Pew Research Center polls, 50% of Americans now support same-sex marriage and 43% are opposed.

This analysis was written by David Masci, Senior Researcher, Pew Research Center’s Forum on Religion & Public Life, and Ira C. Lupu, F. Elwood and Eleanor Davis Professor of Law Emeritus at The George Washington University.