Everything to know about the Respect for Marriage Act and the new battle for same-sex marriage

The House passed the Respect for Marriage Act this week, codifying federal protections for same-sex marriage in the wake of concerns among lawmakers and LGBTQ advocates that the U.S. Supreme Court might reassess its landmark 2015 decision making gay marriage the law of the land.

All 220 House Democrats and 47 Republicans voted in favor. Now the measure heads to the Senate, where it is unclear whether it can win over enough Republicans and advance to the White House.

Worries over the future of gay marriage were sparked by Justice Clarence Thomas’ remarks in his concurring opinion on the court’s overturning of Roe v. Wade in June. Thomas called on the court to also reconsider other so-called rights protected by the Constitution, such as those outlined in the Obergefell v. Hodges ruling protecting same-sex marriage.

Is the national right to same-sex marriage going to be overturned?

Many LGBTQ activists have warned in recent months that a Supreme Court that overturns abortion rights could also remove protections for same-sex marriage.

"In overturning Roe v. Wade, the current Supreme Court showed hostility to individual rights protected by the due process clause of the Constitution," said Brad Sears, founding executive director at the Williams Institute at the University of California, Los Angeles, School of Law.

The ruling, he said, also showed "a willingness to overturn precedent that forms a critical part of how the majority of Americans understand our freedom and society today."

Though there are reasons to fear that a group of conservative justices could overturn marriage equality, Sears said, there are also strong arguments that could lead the court to uphold it – including the court's holding that "people do not rely on the right to have an abortion in order to shape their lives, because unwanted pregnancies are accidental."

"Whatever you think of that reasoning," he said, "it is easy to see how marriage is quite different. Marriage is about reliance."

While it's hard to predict what the court will ultimately do, it's possible state legislators and lower courts could target same-sex marriage in a piecemeal fashion as what happened with abortion rights in recent decades.

"What we thought was settled law will have to be litigated all over again, creating years of uncertainty," Sears said.

What is the Respect for Marriage Act?

The legislation, sponsored by Rep. Jerry Nadler, D-New York, grants protections for same-sex and interracial marriages, repealing and replacing provisions that define marriage as between a man and woman, or that define spouse as someone of the opposite sex. It also repeals and replaces provisions that don’t require states to recognize same-sex unions from other states and allows legal action for violations.

What does it mean to codify same-sex marriage?

According to the Legal Information Institute at Cornell University in Ithaca, New York, codifying means arranging judicial decisions or legislative acts into a systematic code.

Sears, of the Williams Institute, said codifying the act under federal law prevents states from nullifying same-sex and interracial marriages if they were legal in the places they were performed.

"It's likely that over half the states would continue to extend marriage equality to same-sex couples even if the Supreme Court overturned Obergefell," he said. "Many couples would still be able to marry in their home state or a nearby state."

How many same-sex unions are there in the US?

There are about 513,000 married same-sex couples in the United States.

More than half of them have married since the Obergefell v. Hodges decision, Sears said.

What portion of Americans support same-sex marriage?

Survey results published in March by the Public Religion Research Institute show 68% of Americans favor legal marriage for gay and lesbian couples. The figure is 14 percentage points higher than in 2014, when 54% of Americans reported supporting such unions.

Republicans are divided on the question: 48% support it and 50% oppose. Democrats are heavily in favor at 81%, and independents are just behind at 73%.

"Greater visibility of LGBT people and discussion of the issue, even when policy decisions went the other direction, led to more support," Sears said.

Reporter Katherine Swartz contributed to this report.

This article originally appeared on USA TODAY: What does codifying same-sex marriage mean? New battle goes to Senate