WASHINGTON — House Republicans were outraged when President Barack Obama acted without their approval — in fact, despite their explicit opposition — on immigration. Now they have to contend with their own party’s presumptive nominee promising to do the same thing.

GOP presidential candidate Donald Trump vowed again Monday to indefinitely ban Muslims from entering the U.S. after a deadly mass shooting at an Orlando gay nightclub, carried out by an American-born man who authorities say expressed loyaltyto Islamic extremists. For the first time, Trump argued that he would have the authorityto impose a sweeping ban like that with or without Congressional approval.

“The immigration laws of the United States give the president powers to suspend entry into the country of any class of persons,” he said at a Monday event. “I will suspend immigration from areas of the world where there is a proven history of terrorism against the United States, Europe or our allies, until we fully understand how to end these threats.”

It’s doubtful Republican leaders would ever give him that authority, considering they’ve condemned his statements about banning Muslim visitors and immigrants. But Trump’s proposal has put GOP lawmakers in a sticky spot: They have spent years opposing Obama’s executive actions on immigration and even joined a lawsuit to stop him, based on the argument that he was overstepping his constitutional authority. So what do they do with a presumptive nominee who seems as eager to bypass them as they say Obama is?

The Huffington Post asked a number of Republicans on Tuesday if they thought a President Trump could unilaterally ban Muslims from entering the country. Most of them bristled.

“The Constitution is the Constitution — it doesn’t work that way,” Rep. David Schweikert (R-Ariz.) said. “As a member of Congress, we are going to, whether it be a Republican president or a Democratic president, I think we will vigorously defend the fact that we’re Article I,” he added, referring to the statute of the Constitution that puts legislative powers in the hands of the House and Senate.

Rep. Adam Kinzinger (R-Ill.) said he didn’t know whether Trump would have that kind of power as president and emphasized that he opposed the president doing something like that. Kinzinger also said it would run counter to what he called one of Republicans’ “big hopes: reclaiming Article I of the Constitution.”

“At the end of the day, I hope he respects the role of Congress and assume he will,” Kinzinger said.

Rep. Dave Brat (R-Va.) said he hopes Trump won’t actually follow through with the ban, and that he would “walk that back by the time it becomes policy time.” But Brat’s prediction seemed to be based on a hunch rather than any concrete evidence.

The freshman congressman appeared tickled by the idea that his party’s presumptive nominee would start a constitutional debate in Congress over the powers of the presidency.

“We’re all fighting for Article I, and so ... we’re trying to rein in President Obama since the time I got in on unconstitutional amnesty,” Brat said. “We haven’t been able to do that. And the good news is, if this conversation does become full-fledged, it’ll be good to see the Democrats reaching for pocket Constitutions finally. And that’ll make me happy.”

The top House Republican, Speaker Paul Ryan (Wis.), has previously spoken out against Trump’s attacks on Muslims. But on Tuesday, he refused to say if his party’s presidential candidate would have the authority to enact such a ban without congressional approval. He told reporters to look it up themselves.

“That’s a question about immigration law,” Ryan said during a press briefing. “You can go into the 1952 Immigration and Naturalization Act to determine whether or not the president has that kind of discretion.”

(For the record: Legal experts have said Trump’s proposal for a ban on Muslims entering the U.S. would be unconstitutional.)

Some lawmakers showed that if they’ve learned anything on Capitol Hill, it’s that they’ve perfected the art of the dodge.

“I’m not going to be drawn into a debate on whatever it is Mr. Trump says,” said Rep. Mike Conaway (R-Texas). “I’ve got my personal views on immigration, what we should do. You’ll have to talk to Mr. Trump about his.”

“Aw, man. I’m not going to speak to that,” said Rep. Kristi Noem (R-S.D.). “I won’t give you an answer on that today.”

Across the Capitol, Republican senators tried to distance themselves from Trump’s latest attacks on Muslims and questioned whether such a ban would even be legal.

“There are some things that I’ve agreed with Mr. Trump on — he wants to make America great again … There are some things I disagree with, and when there are, we’re not going to defend those comments,” said Sen. Mike Rounds (R-S.D.), slipping into an elevator. “I don’t think you can ban people based on their religious beliefs.”

Asked if he thought a President Trump would have that kind of authority, Rounds laughed. “No,” he said, as the elevator doors closed.

“I don’t agree with him on that,” said Sen. Orrin Hatch (R-Utah). “I don’t know how you do that, since most Muslims in our society are decent and honorable people.”

Sen. Jim Inhofe (R-Okla.) said he’s not really focused on the issue of whether Trump would have the authority to impose a ban on Muslims, and is more concerned about defeating terrorists.

“Aren’t we used to executive overreach already?” he asked, taking a shot at Obama’s actions on immigration. Asked if that means he’s OK, then, with the idea of a President Trump using his executive authority to unilaterally ban Muslims from entering the country, he hedged.

“No,” said Inhofe. “I don’t know about that. No.”

Sen. Ted Cruz (R-Texas), perhaps Trump’s biggest nemesis on Capitol Hill after enduring an ugly presidential primary campaign against him, said only that America needs “a commander-in-chief who is clear-eyed and focused on keeping the country safe.” Asked if he got that sense from Trump’s speech, Cruz stood in an elevator looking at reporters and waited for the doors to close.

Some made it clear they didn’t want to talk about Trump. Like, at all.

“I don’t make any comments on the presidential candidates,” said Sen. Mike Enzi (R-Wyo.). “If you’ve got an issue you want to talk to me about that I’m working on, I’m happy to talk about it.”

Asked if that means he has no thoughts on Trump being his party’s presidential nominee, the Wyoming senator paused, and said, “Not that I’m sharing.”

Trump did have one defender. Sen. Jeff Sessions (R-Ala.), the first senator to endorse Trump, said there was a huge difference between Trump’s statements and Obama’s executive actions on immigration, and that presidents have the authority to dictate who enters the country. He defended the idea of putting more scrutiny on people from certain countries or even halting their entry, but declined to respond  the call to temporarily ban all Muslims from coming to the U.S.

Sessions said his colleagues “are confused a bit” about the matter.

“Some of our members are just confusing that fair treatment we give to all religious persons in America and religious minorities with immigration, which is quite a different subject,” said Sessions, who chairs the Senate subcommittee that handles immigration issues.