In a move that concerned the Fraternal Order of Police, one of Trump’s biggest supporters in the 2016 election campaign, U.S. Attorney General Jeff Sessions said on Monday that the Justice Department would restrict grants to jurisdictions that do not cooperate with federal immigration authorities.

Sanctuary cities, such as San Francisco and New York, refuse to cooperate sometimes by not notifying Department of Homeland Security agents when illegal immigrants are being released from incarceration.

Dozens of local governments and cities have joined a “sanctuary” movement aimed at protecting immigrants. Trump has vowed to crack down on illegal immigration and in general, these cities offer safe harbor and often do not use municipal funds or resources to advance the enforcement of federal immigration laws.

Trump met on Tuesday with police union leaders. Sessions was at the meeting, too, along with Vice President Mike Pence, said Jim Pasco, executive director of the union.