Congressman Stephen Lynch is voicing his opposition to sanctuary cities, which limit cooperation with federal immigration officials.

Lynch advocated for improved federal immigration laws during an appearance on Boston Public Radio today, but said individual cities like Boston shouldn't be able to set their own immigration policies.

"It’s very difficult for Mayor Walsh or anybody else to really discern who should be coming to the country and who should not," he said. "I mean, that’s not the constitutional method."

Boston Mayor Marty Walsh has been a vocal critic of the Trump administration's immigration policies. When President Trump threatened to pull federal funding from sanctuary cities, Walsh said he'd do everything possible to protect undocumented Boston residents, including opening City Hall as shelter for them.

Lynch criticized city mayors for what he said was a lack of uniform immigration enforcement.

"You can’t have 300 mayors running a parallel immigration policy," he said. "You know we’re doing this sanctuary city routine and that’s not good either."

Lynch says enough Republicans in Congress have signed a discharge petition bring several immigration bills to the House floor for debate, despite objections from House Speaker Paul Ryan.

Congressman Stephen Lynch is a ranking member of the House Subcommittee on National Security. He’s a Democrat representing the 8th district.