() U.S. Attorney General Pam Bondi has written to U.S. cities and states with “sanctuary” policies in place, saying leaders could face criminal charges after allegedly obstructing federal immigration enforcement and giving migrants cover to perpetrate crimes.

Bondi sent a letter to Democratic officials, including California Gov. Gavin Newsom, on Thursday after she said that President Donald Trump authorized her to identify “sanctuary” jurisdictions and notify them of their unlawful sanctuary status and potential violations of federal law.

She also wrote Trump directed federal agencies to identify and evaluate their statutory authority to issue grants, contracts and federal funds to determine where conditions could be added to combat “sanctuary policies.”

“Individuals operating under the color of law, using their official position to obstruct federal immigration enforcement efforts and facilitating or inducing illegal immigration may be subject to criminal charges,” Bondi wrote.

Since Trump signed an executive order in April directing the DOJ to create a list of sanctuary jurisdictions, the DOJ has filed several related lawsuits, including one last month against New York City.

Last week, the Department of Justice released a list of 35 “sanctuary” cities and vowed to bring lawsuits against jurisdictions that fail to comply with Trump’s immigration enforcement policies.

Bondi wrote that for too long, “sanctuary” jurisdictions have undermined cooperation between state, local and federal government agencies. That cooperation, she wrote in the letter, is vital to enforce federal law and protect national security.

The letter was sent amid ongoing friction between the Trump administration and officials in cities such as Los Angeles, Chicago, New York and Denver. Chicago Mayor Brandon Johnson, Boston Mayor Michelle Wu and Denver Mayor Michael Johnston have continued to defend their policies after being called to appear on Capitol Hill earlier this year.

In June, 34 cities and counties requested to join a lawsuit brought by California to keep the Trump administration from cutting federal funding based on their policies that limit cooperation with federal immigration enforcement.

Last week, Department of Homeland Security Secretary Kristi Noem referred to Chicago’s mayor and Illinois’ governor as “obstructionists” and said that the two officials routinely place the rights of migrant criminals over the safety of residents.

Bondi wrote in her letter Thursday that in her role as the nation’s top law enforcement officer, she is committed to identifying state and local laws and policies that facilitate violations of federal law or impede lawful immigration enforcement operations. She also directed her office and each U.S. Attorney’s Office to investigate incidents involving “potential unlawful conduct.”