(NewsNation) ⁠— Last week, the Centers for Disease Control and Prevention announced it would end a policy that limited asylum at the U.S.-Mexico border to prevent the spread of COVID-19.

The decision was celebrated among many Democratic lawmakers and immigration advocates but has been criticized by Republicans and some moderate Democrats who fear the rollback will further exacerbate the crisis at the border.

The public health policy, known as Title 42, was enacted under President Donald Trump at the start of the coronavirus pandemic and continued under President Joe Biden. It allowed the government to turn away migrants at the border for public health reasons.

But the policy has been controversial ever since it was implemented. The Trump administration said it would help prevent the spread of COVID-19, but critics argued that it was a misapplication of the law and mainly put in place to block immigration, not to serve public health interests.

Now, the policy is set to end May 23.

The question still being debated: What happens next?

what is title 42?

Title 42 is a provision in the 1944 Public Health Service Act that allows the federal government to ban people from entering the country in the case of a COVID-19-like pandemic. In March 2020, the Centers for Disease Control and Prevention (CDC) enacted the rule under then-President Trump.

The order gave Border Patrol agents the power to turn away migrants on public health grounds. The Trump administration argued that it would prevent the spread of coronavirus, specifically in crowded immigration detention facilities.

But critics said the policy was inhumane and could send people back to countries where they face harm.

The order became especially important for migrants seeking asylum. Under U.S. immigration law, an asylum claim triggers a process that allows migrants to remain in the country to plead their case. But under Title 42, Border Patrol agents could expel migrants seeking asylum without a formal hearing.

Over 1.7 million migrants have been expelled under Title 42 since it took effect in March 2020, according to U.S. Customs and Border Protection (CBP) data. More than 70% of those expulsions occurred after President Biden took office in January 2021.

what’s been the response?

Republican senators, as well as a number of moderate Democrats, have pushed back against Biden’s decision to end Title 42, fearing it will further destabilize the border at a time when migrant encounters are surging.

Border Patrol officials say they are planning for as many as 18,000 arrivals a day once Title 42 expires in May.

Texas Gov. Greg Abbott, who has been a vocal critic of Biden’s handling of the border, said he would offer buses to migrants who wish to go to Washington, D.C.

Earlier this week, the Texas governor directed state troopers to begin stopping and inspecting commercial vehicles that come across the U.S.-Mexico border.

Elsewhere, conservative-led governments in Arizona, Louisiana and Missouri have sued the Biden administration to prevent federal officials from ending the public health rule, arguing that doing so would lead to “chaos” and “catastrophe.”

Others celebrated the change and said the Title 42 rollback was overdue.

“Today is a bright spot in our nation’s history with the end of the Trump-initiated Title 42 policy,” said Rep. Raúl Ruiz, D-Calif., the Congressional Hispanic Caucus (CHC) chair, in a statement. 

The United Nations refugee agency had also called for the U.S. government to end the use of Title 42 at the border.

The number of migrants attempting to enter the U.S. illegally reached its highest level ever last fiscal year, according to CBP data. Border Patrol reported more than 1.7 million encounters at the U.S.-Mexico border, compared to about 460,000 the year prior.

In just the first five months of fiscal year 2022, U.S Customs and Border Protection has reported almost 840,000 encounters, which means 2022 is on pace to surpass 2,000,000 encounters along the southern border.

what does it mean for ukrainian refugees?

President Biden has vowed to take in up to 100,000 Ukrainian refugees but because Title 42 is still in effect, most people seeking asylum can be turned away.

To address the contradiction, last month the Department of Homeland Security instructed CBP to exempt Ukrainians from the order on a case-by-case basis.

That has led to an influx of refugees in Mexico, which many Ukrainians see as their best chance to get to the United States. That’s because it’s much easier to acquire a tourist visa to fly there than it is to travel to America. 

Last week, close to 3,000 Ukrainians entered the U.S. through the southern border, Secretary of Homeland Security Alejandro Mayorkas told CBS on Wednesday. And as the war continues, that number is expected to grow.

But keeping up with that surge could prove difficult. At a pedestrian border crossing near San Diego, 24 officers are hoping to process 578 people a day, Enrique Lucero, the city of Tijuana’s director of migrant affairs, told the Associated Press.

The Biden administration has not outlined an expedited resettlement plan but more details should be available soon, White House press secretary Jen Psaki said Tuesday.

For now, hundreds Ukrainian refugees continue to wait in Tijuana, sleeping in temporary shelters and converted gymnasiums.