U.S. Immigration and Customs Enforcement officers will need preapproval from a senior manager before trying to deport anyone who is not a recent border crosser, a national security threat or a criminal offender with an aggravated-felony conviction, according to interim enforcement memo issued by the Biden administration Thursday.

The narrower priorities are expected to result in a steep drop in immigration arrests and deportations. Biden officials said the new guidelines — which will be in effect for the next 90 days — will allow the agency to make better use of its resources while prioritizing public safety threats.

President Biden, who has rejected calls from liberal Democrats to “abolish ICE,” has taken several measures during his first month to reverse his predecessor’s immigration policies and chart a much different course. Reining in an agency with a reputation for zealous enforcement under President Donald Trump was at the top of Biden’s list.

“By focusing our limited resources on cases that present threats to national security, border security, and public safety, our agency will more ably and effectively execute its law enforcement mission,” ICE acting director Tae Johnson said in a statement. “We must prioritize our efforts to achieve the greatest security and safety impact.”

Republican lawmakers and others critical of Biden’s changes say the narrower priorities will strip ICE officers of discretion while allowing offenders with DUI convictions or serious felonies to remain in the country. The top Republicans on the House Oversight and Judiciary committees sent Johnson a letter this week expressing “serious concerns” about the new priorities.

“These reckless changes — allowing criminal aliens to remain in our communities — place Americans at risk and will undoubtedly lead to many preventable crimes,” Reps. Jim Jordan (R-Ohio) and James Comer (R-Ky.) wrote.

“Scores of individuals who have already proven themselves to be public safety threats by arrest or conviction for serious criminal offenses — such as driving under the influence of alcohol or drugs (DUI), simple assaults, or other crimes that are not considered aggravated felonies — are also not listed as priorities for enforcement,” they said.

The Enforcement and Removal Operations branch of ICE, which is responsible for immigrant arrests, detention and deportation, has a $4.1 billion budget and about 8,000 officers and staff. Under the interim guidelines, ICE personnel will need to seek preapproval from one of ICE’s 24 field office directors before arresting immigrants who fall outside the new enforcement priorities.

The new rules “do not exempt any individual unlawfully in the United States from enforcement” or deportation, Department of Homeland Security officials said, but rather provide clearer directions to the ICE officers afforded broad latitude under Trump.

Those priorities include national security threats such as terrorism or espionage, or immigrants convicted of aggravated felonies including murder, rape, child sexual abuse or drug trafficking. An immigrant whose offense involved participation in a street gang would also be a priority, officials said.

Biden’s narrower priorities will apply to arrests for immigrants being released from prison or jail, as well as “at large” enforcement targeting individuals in their homes and neighborhoods, the officials said. For those arrests, ICE will be required to alert local law enforcement officials of their plans.

ICE officers will also be instructed to consider mitigating factors before making an arrest, such as whether the criminal offense was recent, how long of a jail or prison term the person served, and whether they have ties to U.S. citizen children or other family members.

A review of recent ICE statistics suggests enforcement could decline sharply under Biden’s new priorities. The 93,000 individuals arrested by ICE officers in the U.S. interior last year had more than 374,000 criminal convictions or pending charges on their records, but only about 10 to 20 percent appear to be the kind of aggravated felony convictions that would make them a priority under Biden’s rules, ICE statistics show.

Border crossers who entered the country illegally after Nov. 1, 2020, would also be a priority requiring no preapproval, a provision meant to discourage would-be migrants from viewing the new guidelines as an invitation to attempt the journey to the United States, officials said.

Meanwhile on Thursday, Democratic lawmakers formally introduced Biden’s 353-page immigration reform bill, which includes a plan to grant legal status to approximately 11 million unauthorized workers who are mostly from Mexico and Central America. The U.S. government has not passed a major citizenship bill since 1986, when legislation signed by Republican President Ronald Reagan legalized nearly 3 million undocumented immigrants.

The new legislation appears to face slim prospects in a divided Senate where opposition to legalization — denounced by many GOP members as “amnesty” — hardened under Trump. Members of both parties have unsuccessfully attempted to pass immigration reform many times over the past two decades.

“The reason we have not gotten immigration reform over the finish line is not because of a lack of will,” said Sen. Robert Menendez (D-N.J.), the son of Cuban immigrants and the bill’s sponsor in the Senate. “It is because time and time again we have compromised too much and capitulated too quickly to fringe voices who have refused to accept the humanity and contributions of immigrants to our country.”

Trump often boasted he would free up ICE officers to do their jobs without fear of missteps, likening the new freedom to removing handcuffs placed by the Obama administration. Stories of ICE officers arresting and deporting immigrants after minor traffic violations or on the basis of years-old convictions became commonplace and fueled perceptions of an agency gone rogue.

Under Trump, the vast majority of ICE arrests were immigrants with criminal convictions or pending criminal charges, but most were arrested for offenses such as reentering the country illegally, traffic violations and driving under the influence.

Though Trump promised to deport “millions” when he took office, his administration ended up sending away fewer immigrants than President Barack Obama did during his first term. Trump’s ICE boosterism further politicized the agency and accelerated the “sanctuary” movement by cities and jurisdictions that limit or bar cooperation between their law enforcement officers and federal deportation efforts.

Biden’s new rules require ICE field offices to submit weekly reports to Washington detailing the implementation. A DHS official, who spoke to reporters on condition of anonymity, said the increased transparency and accountability will “provide some opportunities for teachable moments” and dialogue “about what enforcement actions were an appropriate allocation of resources, and where there might be improvements.”