The Michigan GOP lawmaker behind a proposed statewide ban on sanctuary cities was unable to explain how the law would be enforced.

Rep. Pamela Hornberger (R-Chesterfield Township) during a Monday coffeehouse meeting with constituents said the Sanctuary Policy Prohibition Act she introduced last month would not lead to racial profiling, contrary to what officials from concerned groups like the ACLU of Michigan have said.

The bill, known as HB 4105, states that a “peace officer who has probable cause to believe that an individual under arrest is not legally present in the United States shall report that individual to the United States Immigration and Customs Enforcement Office [ICE].”

The measure directs police officers to alert ICE when they have probable cause to believe a person under arrest is undocumented.  When pressed, Hornberger was unable to provide a single example of what might constitute probable cause.

The measure comes as the Trump administration has threatened to withhold federal funds from self-identified sanctuary cities as part of its anti-immigration agenda.

The bill, which prohibits municipalities from passing polices to limit cooperation with federal immigration officials, would require local governments to submit an annual count of its ICE referrals to the Michigan legislature. Local governments that fail to comply will lose funding they typically receive under the Glenn Steil State Revenue Sharing Act of 1971.

Kimberly S. Buddin, policy counsel at the ACLU of Michigan, told Rewire last week that the bill was unconstitutional and would end “policies that have established trust between police and the communities they serve by further increasing racial profiling. “

Several residents and activists at the meeting asked Hornberger about her motivation for the bill and emphasized its potential impact on local communities. Hornberger told the group she did not have statistics or know of any instances in which police agencies were breaking the immigration-enforcement laws already in place.

“This isn’t asking the police to act any other way than they already do,” Hornberger said.

Sophia Softky, a Detroit activist, asked how the state would differentiate municipalities that report no ICE referrals simply because they had none from those that chose not to report referrals to protect their community’s undocumented residents.

“I think a really big concern a lot of us have is that if there isn’t a clear way to demonstrate compliance, police officers in different municipalities might feel free pressure to try to demonstrate compliance by making specious arrests, and those arrests—especially if you can’t even define probable cause for being in the country illegally—that opens them up to being litigated for racial profiling,” said Softky, co-founder of the Detroit Sanctuary Committee. “This is a huge problem. This exposes police officers to getting sued for racial profiling.”

The Republican measure would have major implications for Detroit, Michigan’s most populous municipality and home to the state’s largest population of Latinos.

Although staff for Detroit Mayor Mike Duggan has said the city fully cooperates with federal agencies regardless of a person’s immigration status, city council member Raquel Castañeda-López has called the municipality a “sanctuary city.”

Christin Lee, a volunteer for Detroit’s Freedom House, made an emotional appeal to have the bill retracted, saying that it demonizes undocumented people who are already terrified for their lives.

Located at the end of the Ambassador Bridge connecting Detroit to Canada, Freedom House provides temporary housing and legal services to asylum seekers. Lee said Freedom House faces an uncertain future after the federal housing department failed to renew an annual grant that funds over half the nonprofit’s budget.

Chesterfield resident Susan Griffith, who serves as vice chairperson of the Macomb County Democratic Committee, asked Hornberger why she would introduce the bill knowing that Lansing, the state’s capital, was in the process of becoming a sanctuary city. Hornberger said she was “not sure” which municipalities in Michigan were considered sanctuary cities.

Hornberger told Rewire she would meet with ACLU officials this month to discuss the bill.

If passed, HB 4105 would go into effect 90 days after the date it is enacted. Republicans control both chambers of the Michigan legislature.

The four police officers who attended the event didn’t speak. An officer from the New Baltimore Police Department told Rewire that law enforcement presence was customary at public gatherings with legislators.