Who is Markwayne Mullin, named by Trump to replace Kristi Noem as Homeland Security secretary?

By Michael Williams, CNN

(CNN) — President Donald Trump on Thursday announced he was ousting Department of Homeland Security Secretary Kristi Noem, and that GOP Sen. Markwayne Mullin of Oklahoma would replace her.

Mullin, a first-term senator who has served in that role since 2023, is a former mixed-martial artist and business owner who is a strong supporter of Trump’s hardline immigration policy.

An enrolled member of Cherokee Nation, Mullin is the first tribal citizen to serve in the US Senate in nearly two decades.

He will inherit an agency that is an integral cornerstone to Trump’s domestic policy agenda – the most well-funded federal law enforcement agency in the country and one which has come under intense scrutiny during the first year of Trump’s second term for how it has conducted itself.

Here’s what to know about Mullin:

Immigration hardliner

Shortly after Trump announced his intention to have Mullin serve as Homeland Security secretary, Mullin said his focus would be to “keep the homeland secure.”

“There’s a lot of work we can do to get the Department of Homeland Security working for the American people,” Mullin said. “The Department of Homeland Security has a very broad jurisdiction, and I think there’s a lot of work that we need to do and I’m excited about it.”

His past public comments have shown that he is closely aligned with Trump’s agenda.

Following a Supreme Court decision last year that was intertwined with Trump’s executive order ending birthright citizenship, Mullin said on NBC’s “Meet the Press” that babies born in the US to undocumented parents should also be expelled from the country – framing that position as a desire to keep the children with their parents.

“Why wouldn’t you send a child with their parents?” he told NBC’s Kristen Welker, “I mean, why would you want to separate them?”

He accused some immigrants who come to the US and have children of being part of an “industry” that seeks to game the system.

“‘There’s a whole industry that stood up to bring people here in their last month of pregnancy to have a child here, and they come here on a vacation visa, and they have a child so their child will be able to be US citizens,” he said.

In an interview with CNBC last month, Mullin said everyone should carry proof of citizenship in case they are stopped and questioned by law enforcement: “There’s nothing to hide if you’re here legally,” he said.

Mullin defended the fatal shootings of Alex Pretti and Renee Good in Minneapolis at the hands of federal immigration officers earlier this year.

Shortly after Good was shot by an Immigration and Customs Enforcement agent, Mullin said the officer “didn’t have an option” but to “engage” Good, who was driving a vehicle that he said should be viewed as a deadly weapon.

Pugilistic senator

Mullin wrestled in college and fought briefly as a professional mixed martial artist.

He has taken his fighter’s spirit to Capitol Hill. During his time in the House, Mullin was famous for his intense, MMA-style workouts that he used to run for other members of Congress.

Mullin was serving in the House during the January 6, 2021, attack on the US Capitol and assisted officers in barricading the doors to the House floor. He later said he told the rioters he would deal with them physically if they broke through.

Years later, as Trump mulled about the possibility of pardoning the rioters, Mullin urged Trump to “look at the facts before he does something” and said that anyone who attacked police needed “to pay for that, without question.”

Trump pardoned them anyway. After those pardons, Mullin said on CNN there was “no question” the siege of the Capitol was a “riot” and a “horrible day.”

But he added: “However, the American people have chose to move on” by electing Trump in spite of his campaign trail discussions about pardoning the rioters.

During a 2023 Senate hearing, Mullin challenged a witness, Teamsters boss Sean O’Brien, to a fight. The pair had a history of testy exchanges.

He later told CNN that a return to physical violence could help cure people whom he described as “keyboard warriors” who “go out there and run their mouth all the time, and then they don’t ever have to face the consequences.”

What happens next?

Trump announcement of Mullin’s ascension to DHS secretary was somewhat vague. Noem said her last day would be March 31, 2026, and the president said Mullin “will become” DHS secretary that same day.

But that’s not Trump’s decision to make because the position requires Senate confirmation.

If Mullin is not confirmed by March 31, the position would need to be filled by an acting secretary. But that can’t be Mullin “for a couple of reasons,” said Thomas Berry, the director of the Cato Institute’s Robert A. Levy Center for Constitutional Studies who has written extensively about presidential appointments.

The law requires someone to have some other job in the executive branch before they can become the acting secretary of an agency. Mullin can’t do that because he’s currently serving in the Senate.

“The only way he could become an acting is if he resigned his Senate seat first, got a new job in the administration, got some non-Senate-confirmed position, and then potentially you could try a maneuver to make him the acting,” he said.

But Berry added that move would be legally dubious due to previous litigation after similar maneuvers were attempted.

In the case where March 31 passes and Mullin is not confirmed, the law calls for the deputy secretary of DHS to become the acting secretary. The White House seems confident that Mullin would be able to be confirmed before then.

There’s also the case of Mullin’s Senate seat. Once he resigns, Oklahoma law gives Gov. Kevin Stitt 30 days to appoint a replacement. Since Mullin is a Republican, his replacement would have to have been a registered Republican for at least five years. The appointee would also be required to submit an oath that they will not run for the seat when it comes up for election.

Because Mullin is scheduled to be up for reelection in November, there won’t be a separate special election.

Instead, the winner of November’s election will be eligible to take office once the results are finalized.

CNN’s Ethan Cohen, Morgan Rimmer, Lauren Fox and Sarah Ferris contributed to this report.

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