(NewsNation) — A judge has ruled in favor of dozens of Republican states seeking to prevent the Biden administration from ending a pandemic-era immigration rule. Conservatives say the rule, or something like it, is crucial to avoid an unmanageable surge of migrants at the southern border.

“I am so proud of the lawyers from our office who just got a Temporary Restraining Order to keep Title 42 in place,” tweeted Arizona Attorney General Mark Brnovich on Monday. “We will continue to fight the Biden administration’s open border policies.”

Title 42 is a regulation that allows Customs and Border Patrol agents to turn away migrants with the goal of preventing the spread of disease. Critics say the rule, which dates back to the 1940s, was not meant to be used as the backbone of immigration policy. But proponents argue lifting it would rob CBP of one of the only tools it has to turn migrants away as it logs encounters at the border not seen since the turn of the century.

Title 42 was set to expire May 23.

House Republican leader Kevin McCarthy led a group of GOP lawmakers to the U.S.-Mexico border in Texas on Monday, speaking out against the Biden administration’s decision to let Title 42 expire.

“If President Biden lifts Title 42, what we see today will be much worse,” McCarthy said. “A country without a secure border is not a country. And no longer is it just border cities. Every city in America is a border city.”

President Joe Biden’s announcement that Title 42 might expire has sparked a policy feud and faces growing division even within the Democratic Party.

Nine lawmakers, including two other members of House GOP leadership, were expected to join McCarthy in Eagle Pass, Texas as they toured border facilities and observed conditions firsthand.

McCarthy said repealing Title 42 will further destabilize the border at a time when migrant encounters are surging.

“It’s not just unsustainable now; it’ll be uncontrollable then,” McCarthy said.

Republicans have made it clear they intend to make immigration and border security pillars of their midterm campaign.

Homeland Security Secretary Alejandro Mayorkas is scheduled to testify before the House Judiciary Committee for the first time Thursday and Republicans hope to get him to personally address the immigration issues.

The Trump administration has said Title 42 would help prevent the spread of COVID-19, but critics argued that it was a misapplication of the law — mainly put in place to block immigration, not to serve public health interests.

“If the public health crisis is abating, then it would seem that the reasoning for Title 42 would be operative is ending,” said retired U.S. Air Force Major General William Eynart. “I mean, you can’t have it both ways. You can’t say, ‘Oh, the pandemic is over … but we’re gonna keep Title 42 In effect.’”

Rep. Randy Weber (R, Texas) told NewsNation it should be in place as long as there is any chance of COVID-19 being spread, no matter how small.

“Yes, there are limited cases of illegals coming over with COVID, but they do come over and they do have COVID,” he said.

The development comes as the Biden administration recorded roughly 221,000 migrant arrests at the southern border for the month of March — the highest monthly number of border encounters in two decades.

White House press secretary Jen Psaki confirmed last week that the Biden administration was preparing for the end of Title 42 on May 23.

“The president agrees that immigration in our country is broken,” Psaki said.

On the day Republicans toured the border in Eagle Pass, search crews recovered the body Monday of Texas National Guard member Bishop Evans, who went missing after jumping in the Rio Grande on the border to help a migrant struggling to swim across.

Also Monday, Mexican President Andres Manuel Lopez Obrador urged Latinos in the U.S. not to vote in November’s midterm elections for politicians who have “mistreated” them.

The statement was said in response to a comment by former President Donald Trump, who boasted at a rally in Ohio over the weekend that while in office, he had forced Lopez Obrador to deploy 28,000 soldiers along the U.S.-Mexico border to keep out migrants after threatening to slap tariffs on Mexican goods.

Asked about Trump’s comments, Lopez Obrador said no U.S. political party should “use Mexico as a pinata.”

The Hill, Associated Press and Reuters contributed to this report.