Congress has officially passed historic protections for same-sex marriage, establishing a critical safeguard if the Supreme Court were to overturn its 2015 decision guaranteeing this right.

The bill, known as the Respect for Marriage Act, doesn’t go as far as Supreme Court precedent does, though it provides an important contingency in case that ruling, Obergefell v. Hodges, is ever struck down. Notably, the legislation requires states and the federal government to continue to recognize same-sex marriages regardless of what the Supreme Court chooses to do.

That provision, ultimately, means Americans in same-sex marriages are shielded from states invalidating their unions and the federal government discriminating against them if past precedent were to fall.

With the act’s passage nearing, here are the answers to four key questions about what the legislation does — and doesn’t — do.

What is the status of same-sex marriages now that the Respect for Marriage Act has passed?

Currently, the right to same-sex marriage is firmly established across all 50 states by the Obergefell decision issued by the Supreme Court in 2015.

However, following the Court’s overturn of Roe v. Wade in their June Dobbs v. Jackson Women’s Health Organization decision, some lawmakers worried same-sex marriage protections could be revoked next. A concurring opinion from Justice Clarence Thomas in the Dobbs case only raised concerns that the court could revisit this case, prompting Congress to quickly advance the Respect for Marriage Act.

The act reaffirms some of Obergefell’s protections by mandating that states and the federal government always recognize same-sex marriages as legally valid.

Prior to that Supreme Court decision, a provision in the Defense of Marriage Act allowed individual states to decide if they would recognize same-sex marriages performed in other states. This bill explicitly targets that loophole. If a couple was married in a blue state that protected same-sex marriage, but moved to a red state that barred it, for example, the red state would still have to recognize their marriage as legally valid.

What the bill does not do, however, is require states to issue marriage licenses to same-sex couples, something that Obergefell guarantees. Because of that, states, more than 30 of which still have same-sex marriage bans on the books, would be able to refuse to issue same-sex marriage licenses, forcing couples to travel elsewhere to obtain them.

“It’s an important first step,” Sen. Elizabeth Warren (D-MA) told Vox, of the bill. “We could go one step further and ensure that every state provides an opportunity for equal marriage, but that will have to wait for another day.”

According to legal experts, Congress stopped short of codifying Obergefell because a bill like that is more likely to face court challenges and be struck down. Since such legislation would require states to issue marriage licenses, it’s also likely it would have received less Republican support because it could give the federal government more jurisdiction on the subject.

The Respect for Marriage Act also officially repeals the Defense of Marriage Act, which defined marriage as a legal union between a man and a woman and prevented the federal government from recognizing same-sex marriages.

While DOMA’s provisions were struck down in the 2013 Windsor v. United States decision and the 2015 Obergefell decision, this bill makes it clear that they can’t be reinstated. In doing so, it codifies federal recognition of same-sex marriages, which is vital for access to more than 1,100 government benefits related to social programs, taxes, and immigration services.

Could Obergefell actually be overturned? What would happen then?

Since Obergefell is a precedent established by the Supreme Court, the justices could decide to overturn it like they have with other precedents like Roe. This bill does not prevent them from being able to do so, but it offers protections for people in case that were to happen.

Civil rights activists have been worried about this possibility given Thomas’s opinion. Other justices, including Samuel Alito and Brett Kavanaugh, however, have stated that the Dobbs decision is not an indication that the court intends to consider other precedents that rest on similar reasoning, as Obergefell does.

Could this bill get challenged in court?

Although many legal experts note that the arguments for challenging the Respect for Marriage Act aren’t necessarily the strongest, it could still face legal action.

According to Katherine Franke, a law professor at Columbia University, states that want to bar same-sex marriage and do not want to recognize marriages that took place in other states could try to claim that Congress does not have the authority to require them to. It would be a longshot for a case like that to be successful, however, she says.

“It would be a radical step for a court to find the Respect for Marriage Act unconstitutional as an illegal exercise of congressional power,” Franke told Vox. “It’s just that with the radicals on the Supreme Court and in lower federal courts, it can’t be ruled out.” For those interested in undermining the bill, these challenges could be levied even if Obergefell remains intact, says Franke.

Does all of this apply to interracial marriage as well?

The legislation states that the same protections it provides for same-sex marriage apply to interracial marriage as well.

The right to interracial marriage was established by the Loving v. Virginia case in 1967, which overrode state-level bans on interracial marriage, and is another precedent that some civil rights advocates worry could be threatened by the Supreme Court following the Dobbs decision.

Were this precedent rolled back, the Respect for Marriage Act would require states and the federal government to recognize interracial marriages, and give those in such unions the same rights and benefits as those in same-sex marriages. As with same-sex marriages, the law would not require states to issue licenses for interracial marriages if they decide to restrict it.

Update, December 8, 2:30 pm ET: This story was originally published on December 2 and has been updated to reflect House passage of the Respect for Marriage Act.