As evidence mounts that Saudi Arabia had a hand in the disappearance of a journalist, there’s a growing rift between President Trump and Congress on what to do about it.

Trump, as he often does when strongmen are involved, is giving Saudi Arabia the benefit of the doubt that its leaders did not order Jamal Khashoggi killed. “Here we go again with you’re guilty until proven innocent,” Trump told the Associated Press.

Meanwhile, House Speaker Paul D. Ryan (R-Wis.) told CBS “This Morning” that the disappearance is “really disturbing” and seemed ready to tee up action to punish Saudi Arabia for it. “If this is the case, it’s atrocious, and we have laws for this,” Ryan said.

But what could Congress do, especially if Trump isn’t on board? It has really only stood up to him in a substantial way on foreign policy once, when it forced him last year to reluctantly sign a bill sanctioning Russia over election interference.

Lawmakers have a number of tools to use against Saudi Arabia, said Jon Alterman, the head of the Middle East Program at the Center for Strategic and International Studies. That’s because Saudi Arabia is particularly sensitive to any deviation from the norm in U.S.-Saudi relations.

“The U.S.-Saudi relationship is more important to Saudi Arabia than it is to the U.S.," Alterman said, “and reinvigorating that relationship had been one of the core accomplishments of [Saudi Crown Prince Mohammed bin Salman].”

But to take the most serious action, Congress will need to convince Trump. Here’s a look at what Congress can do and how Trump fits into it.

Force Trump to sanction Saudi officials, including Mohammed: This is the most obvious tool at Congress’s disposal, because both Congress and the president can levy sanctions. It’s also the most severe and targeted punishment. The likeliest form this would take would be via the Magnitsky Act, which Ryan specifically mentioned in his interview with CBS.

Originally focused on Russia, the law basically allows the United States to sanction foreign officials who commit any human rights violation, explained Jordan Tama, an associate professor at American University’s School of International Service. That could mean a travel ban or freezing assets of top Saudi officials.

A bipartisan group of senators have already asked Trump to consider doing this for Mohammed. And under the law, Trump has four months to respond on whether he will. Another option is for Congress to try to pass sanctions on its own with a veto-proof majority.

Deny any new arms sales to Saudi Arabia: Trump’s first foreign visit was to Saudi Arabia, and shortly after he announced a massive (yet overstated) deal to sell U.S. weapons and defense equipment to the country. That’s one reason the president keeps giving when he explains why he’s reluctant to punish Saudi Arabia.

But Congress has a role here. They have to be notified 30 days before any international arms sale, and they can reject it by passing a law prohibiting the sale. They would need veto-proof majority if Trump is adamant about pushing the sale through.

There’s evidence they could have it. Congress has been wary about Saudi Arabia’s involvement in neighbor Yemen’s civil war and last year narrowly approved arm sales to Saudi Arabia after Sen. Rand Paul (R-Ky.) led an effort to reject it.

Paul said he’s planning to force a vote on this the next time an arms sale to Saudi Arabia comes around: “If they’re responsible or even if there’s any indication that they’re implicated in killing this journalist that was critical of them, we’ve got to stop sending them arms,” Paul told Kentucky radio station WHAS last week.

Hold fast on a terrorism law that Saudi Arabia hates: In 2016, Congress passed into law a bill allowing families of Sept. 11, 2001, victims to sue Saudi Arabia for what some families claim is the country’s collusion in the attack. The law, the Justice Against Sponsors of Terrorism Act, is controversial. It passed over President Barack Obama’s veto and over widespread international concern about lawsuits between civilians and nations. But despite the global controversy the law stirred, Congress can refuse to revisit it and even tighten the screws on Saudi Arabia.

“There are any number of provisions they can attach to laws which could expose Saudi Arabia to [9/11] claims,” Alterman said.

Hold hearings: While Congress doesn’t have prosecutorial power, hearings are its equivalent of a presidential bully pulpit. Congress has asked Trump to launch an investigation into the disappearance of Khashoggi. But several committees in Congress can do this, too.

Through those hearings or other public events, Congress can highlight things the Saudis don’t want highlighted, Alterman said. Issues like women’s freedom, religious tolerance, free speech in Saudi Arabia, human rights and executions. “There are any number of things Congress can do to shine a light on the differences between Saudi Arabia and the U.S.”