() President Donald Trump has vowed to “end” sanctuary cities, putting a stop to laws preventing local law enforcement from being involved in federal immigration enforcement.

John Sandweg, former acting director for Immigration and Customs Enforcement for the Obama administration, joined to discuss what that could mean.

“The sanctuary cities have been a burr in the saddle of the Trump administration,” Sandweg said. “What I would expect here would be something that is tied to the leverage he has against states and localities.”

The main leverage Trump has in getting states or cities to change policies is federal funding.

“What I would expect is something that explicitly says, if you’re a sanctuary city, then we’re going to restrict access to those funds in a real draconian and aggressive way,” he said.

With many cities and states relying extensively on federal funding, that could be enough to get localities to change the law.

The administration has also cracked down on immigration in other ways, including efforts to get the IRS to cooperate with ICE.

Sandweg identified two ways the IRS could be involved.

One is criminal investigations for identity theft or Social Security fraud, where people without documents may falsely use Social Security numbers belonging to U.S. citizens.

“There’s no restriction on information sharing that inhibits federal law enforcement from doing that,” Sandweg said.

The second way the IRS would be of use would be identifying addresses, Sandweg told , to help ensure ICE knows where people live. That could be more of a challenge because of restrictions on sharing civil taxpayer information.

However, getting accurate addresses would increase the number of potential arrests if ICE were able to locate people quickly rather than having to track them down if they have moved.

“I think what ICE is going to be doing is saying, ‘Hey, can you confirm these addresses on these targets?'” Sandweg said.