Gay rights advocates had huge victories recently. Three states legalized gay marriage on election day, and just a few months earlier the president himself endorsed same-sex marriage.

But the U.S. Supreme Court's decision to take up two huge gay marriage cases could set back the gay rights movement years if things don't go its way.

The high court is expected to overturn the Clinton-era Defense of Marriage Act, which bars the federal government from recognizing same-sex marriages.

However, the outcome of the other gay marriage case, involving California's Proposition 8, is less certain.

The justices are reviewing the Ninth Circuit appeals court's ruling that Proposition 8, a voter-approved ban on same-sex marriage, was unconstitutional.

Here are some of the ways the high court could hurt gay rights if it overturns the Ninth Circuit, according to UCLA law professor Adam Winkler, who discussed the possible outcomes with Business Insider:

  • First off, it would be a huge symbolic defeat. "The court helps shape our notions of right and wrong, and here the court would be saying it's okay to discriminate people on the basis of their sexual orientation," Winkler said in an email message.
  • Two, an opinion striking down the Ninth Circuit and affirming Proposition 8 could be used to uphold other anti-gay laws or even adopt new ones, according to Winkler.

"If, say, the court were to hold that sexual orientation discrimination need not be justified by strong government interests, then state and local governments would point to that in defending other types of sexual orientation discrimination, such as adoption bans," Winkler said.

  • Three, gay people couldn't get married in the nation's most populous state -- California.
  • Four, Winkler said, it would create a high court precedent that could take years to overturn and force a lot of gays and lesbians to wait a long time to get married.

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