In an executive order signed last week, President Donald Trump said his administration would cut off federal grant funding to “sanctuary jurisdictions,” saying places that shelter people who lack legal status in the U.S. “have caused immeasurable harm to the American people and to the very fabric of our Republic.”

The order could cover cities, counties and even entire states, and it dovetails with Trump’s promise of swift mass deportations.

Maine has one of the country’s smallest populations of undocumented immigrants, so the Trump policy will likely not have broad impact. Where it could be felt most is Portland, a diverse city with a reputation of welcoming immigrants.

Many in Portland fear Trump’s immigration crackdown could mean friends and neighbors will be deported. Even though former President Barack Obama deported a record 2.4 million people during his terms in office, Trump’s promise of more deportations and a ban on travel to certain countries have prompted a deep, public anxiety in the city unlike anything from the last eight years.

Portland’s current policy states it will cooperate with federal authorities to enforce immigration laws. Some are pushing the city to change this policy, while officials also are pointing to the strength of the existing immigrant protections and the practical limits on local law enforcement’s involvement with immigration officials.

In the background, Gov. Paul LePage has repeatedly labeled the city a sanctuary — for its defiance of his efforts to end aid to asylum seekers — which creates a powerful perception, regardless of Portland’s actual policies.

It’s unclear whether and how Portland would be affected by the Trump order because the federal government has so far failed to specify how it’s going to act. This uncertainty is making the stakes feel high.

Here’s what we know and what we don’t about the local debate over Trump’s planned crackdown on undocumented immigrants and the cities that protect them.

What is a sanctuary city?

There is no settled legal definition of a sanctuary city or jurisdiction, so the term has become something of a political projectile.

Most broadly, the term refers to local governments that extend political and practical protections to people who are in the country without legal status.

Some of America’s largest cities are self-proclaimed sanctuaries, and several smaller New England cities have taken up the tile and changed their policies in acts of open opposition to Trump.

Collectively, they could lose billions in grant money if the Trump administration follows through on the order, which left the details about implementation vague. But several cities have pledged to maintain their policies in defiance of the administration. San Francisco already has sued, arguing the crackdown violates states’ constitutionally protected right by attempting to “commandeer state and local officials to enforce federal law.” The case, which may turn on core constitutional questions, is unlikely to move quickly.

The policy that has come to the center of the political fight over sanctuary cities is whether local law enforcement work with federal immigration authorities. Cities including Chicago, New York and Los Angeles, for instance, limit cooperation with the feds even to the point of refusing requests — known as detainer orders — to hold undocumented inmates in jail.

In his executive order, Trump said the secretary of the Department of Homeland Security can designate a place to be a sanctuary jurisdiction, but the term was not defined. The Department of Homeland Security did not respond to repeated requests for clarification.

Is Portland a sanctuary city?

Local officials in Portland have been denying that the term applies for at least as long as LePage has been making political hay of labeling it as one.

Portland has an explicit policy of cooperating with federal law enforcement, but local police don’t have the power to enforce federal laws. So if federal immigration officials asked Portland police to lend a hand with an arrest, local officers might offer back-up, such as a squad car parked out front of the building where people were being arrested, but they wouldn’t be putting on the cuffs, according to a city spokeswoman.

Trump’s order empowers the secretary of Homeland Security to deputize local law enforcement “to perform the functions of immigration officers in relation to the investigation, apprehension, or detention of aliens in the United States.” Such a move would require “consent of state or local officials,” according to the order.

Portland also has a policy that bars municipal employees — including police — from asking someone about his or her immigration status unless required by law. The policy makes exception for cases when officials have “reasonable suspicion” that someone has committed a felony or previously was deported from the U.S.

This policy alone is enough to categorize Portland as a sanctuary city, according to the Center for Immigration Studies, a Washington based group supportive of Trump’s immigration policy. Jessica Vaughan, the group’s director of policy studies, claims that this policy is “a clear violation” of federal law.

Portland’s lawyer declined to comment on whether the city’s ordinance is consistent with federal law and a spokeswoman said the federal government has not contacted the Portland about the matter.

What’s the impact of Portland’s policy?

City officials and politicians say Portland’s policy offers significant protection to people who might be subject to deportation. It was created in 2003 in “response to federal raids targeting undocumented immigrants in our Latino community,” according to City Councilor Jill Duson.

Enacting a policy not to cooperate with federal officials also could cost the city big bucks. Last year, Portland reportedly received about $30 million in federal funding, according to the Press Herald, though it is unclear how much money the Trump administration could cut off.

And Portland’s policy needs differ from those of places such as San Francisco or Chicago because it does not operate a city jail. Portland brings people arrested to the Cumberland County Jail, meaning there would be a very narrow window in which federal authorities might issue the police a detainer order.

The county also cooperates with federal law enforcement. Last year the jail held 40 inmates for federal immigration authorities, according to Sheriff Kevin Joyce. However, all these people had been arrested by Immigration and Customs Enforcement, not local police, Joyce said.

In his 30-year tenure, the sheriff said he could only recall one case when the the feds had asked the jail to hold someone arrested by local law enforcement.

The Pew Research Center in 2012 estimated Maine to be among the states with the fewest unauthorized immigrants. It had fewer than 5,000, Pew found.

What happens next?

In Portland, lawmakers have so far taken the position that the current protections are sufficient. But several online petitions have been circulating asking city leaders to go further in their protection of undocumented immigrants.

A petition circulated by Progressive Portland — a recently founded group, headed by political organizer Steven Biel — calls on city leaders to “refuse to cooperate with Trump’s illegal and unconstitutional attacks on immigrants and Muslims.” It has received more than 1,500 signatures since being posted over the weekend.

Another petition, opened by Portlander Anna Keller after the election, initially made equally broad requests but has been updated to ask “Portland and the Cumberland County Sheriff’s Department to adopt a policy of not complying with immigration detainer requests.”

Keller said she understands that the city taking this stance might imperil the millions of dollars Portland receives in federal grant funding and that city police are unlikely to receive detainer orders because they do not house inmates.

But she pointed to San Francisco’s lawsuit — and the long legal process that could follow — as evidence that the executive order is unlikely to be enacted and noted that Portland already is being labeled a sanctuary city.

“Proactively conforming to what [the Trump administration] threaten[s] to do, when their policies are so beyond the pale, isn’t a course that we want to take,” Keller said.