“In free democracies, you can’t jail people for opposing the president’s policies, policies that courts have found to be lawful,” said Vanita Gupta, the chief executive of the Leadership Conference on Civil and Human Rights and the former head of the civil rights division of the Justice Department.
Presidents who have sought to intrude on the independence of the Justice Department have for decades been rebuked. President Trump has appeared to frequently cross that line, calling for investigations into Hillary Clinton and one of her aides and demanding that a career F.B.I. official politically aligned with her be removed from his job.
Talk of criminal charges for elected officials also exacerbated tensions between Mr. Trump and local politicians who disagree with his administration’s stance on immigration law enforcement, particularly in California, a state whose liberal residents have become a symbol of staunch opposition to much of the president’s agenda.
Last year, the Trump administration also threatened to withhold federal funding to sanctuary cities, including $28 million in law enforcement grants to state and local jurisdictions in California. In response, both the state and the city of San Francisco sued the administration. California Attorney General Xavier Becerra called the threat to withhold money “bullying.”
More recently, the state Legislature passed the California Values Act, which restricts cooperation with federal immigration agents. The law took effect on Jan. 1, drawing the ire of Thomas Homan, the acting director of Immigration and Customs Enforcement.
Mr. Homan said during an interview with Fox News days later that he had asked the Justice Department to “look into criminal charges for elected officials with sanctuary policies.” He also said that California officials should expect to see more ICE agents and deportation officers in the state.
“In every area, this administration has violated the norms of civil discourse and civil behavior,” said Darrell Steinberg, the mayor of Sacramento and an outspoken opponent of the Trump administration’s immigration policies. “There is a difference between the give and take of partisan politics and what we are witnessing today.”
The city of Sacramento has filed briefs supporting lawsuits against the administration and has allocated more money to immigration services.
Ms. Harris and Ms. Feinstein asked Mr. Sessions to provide communications between the Department of Homeland Security or the White House asking the Justice Department to look into criminal charges for elected officials in sanctuary cities.
The senators said that they did not know of other cases “where duly elected state officials have been placed under threat of arrest and federal prosecution” for acting on the laws that their state legislatures have passed. They also asked that the Justice Department provide the legal basis it would use to prosecute politicians in sanctuary cities.