State law enforcement officials have the "inherent" authority to arrest and hold immigrants scheduled for deportation, a Department of Justice attorney argued in court on Tuesday.

The Supreme Judicial Court has called into question a tool federal immigration authorities use to gain custody of immigrants in the country illegally: requests for state law enforcement to hold someone for federal authorities without a judicially approved warrant.

The case of Commonwealth v. Sreynuon Lunn is moot for the defendant who was taken into custody by Immigration and Customs Enforcement, but it could have broad implications politically and policy-wise as the nation wrestles with heightened efforts to enforce immigration laws.

Lunn entered the United States as a refugee in 1985 and received lawful permanent resident status in the early 1990s, but he racked up a criminal record in the early 2000s and was ordered deported to Cambodia, Joshua Press, an attorney for the Department of Justice told the court. Cambodia would not accept Lunn back, and he was released from federal custody in October 2008, according to a Department of Justice brief, which said almost exactly eight years later Lunn was arrested on unarmed robbery charges, which allegedly occurred in Boston, and Immigration and Customs Enforcement (ICE) lodged a detainer request with state authorities. An immigration detainer included in one of the briefs lists Lunn's citizenship as Thailand and said he was born in 1985.

On Feb. 6, state prosecutors elected not to prosecute Lunn on the robbery charges and the case was dismissed from Boston Municipal Court, according to court documents. Lunn's attorney asked for him to be released but the judge rejected that, and he was placed in the courthouse lockup until ICE agents took him into custody several hours later, according to an affidavit Lunn signed.

Representing the state and the county sheriff, Jessica Barnett, deputy chief of the Criminal Appeals Division for Attorney General Maura Healey, told the justices that state officials cannot arrest and detain someone for a civil immigration infraction without a judicially issued warrant, essentially arguing that the Boston Municipal Court Judge Michael Coyne had overstepped his bounds.

"What they cannot do is perform a warrantless arrest and to detain that person longer than he or she would otherwise be held in state custody," said Barnett. She said state officials can notify ICE about when a defendant is scheduled to be released but cannot delay that person's release from state custody to accommodate federal authorities.

Press argued that without any law prohibiting state officials from detaining people at the request of ICE, the authorities have that power.

"You have that power and as we understand it no law has circumscribed the state or the Commonwealth's power to cooperate with the federal government in these matters," Press said. "Without having any sort of identified limit then if the Commonwealth or its officers - or in this case, the Boston Municipal Court - wants to cooperate with the federal government, we don't see any particular reason why that cannot happen."

Chief Justice Ralph Gants challenged Press to identify specifically where the state obtained its "inherent authority" to detain people at the request of ICE.

"Inherent in our constitution? Inherent in natural law?" Gants asked.

"It's included in the constitution itself and the concept of sovereignty," said Press, who conceded that the power is "not there specifically," but neither is it specified in the federal Constitution.

Emma Winger, an attorney for the Committee for Public Counsel Services representing Lunn, asked the court to go further than Barnett's suggestion that state officials lack statutory authority to hold people on ICE detainers. Winger said a hypothetical act of the Legislature to grant state officials that authority would contain "constitutional violations" because the process lacks judicial oversight.

"That legislation would be improper," Winger said. She said, "All declarations of liberty rest in the hands of the judiciary and the judiciary does not have its hands on arrests under detainers."

In its brief, the Department of Justice said that under an ICE policy issued in March, ICE detainer requests must be accompanied by an administrative warrant signed by an immigration officer. Barnett said the new ICE policy does not change her position that officials lack statutory authority to comply with the detainers.

Press said Lunn's 2008 deportation order was issued by a U.S. immigration judge and Lunn has "no right to be in the United States."

Barnett said ICE previously released Lunn because the country of origin would not accept him and the government cannot detain him indefinitely. She said that "very well might" happen again.

Lunn was ordered deported under President George W. Bush, arrested on state charges during the presidency of Barack Obama, and is now under ICE custody as the immigration debate has reached fever pitch under President Donald Trump.

Bristol County Sheriff Tom Hodgson testified before Congress last month that elected officials in "sanctuary cities" that seek to limit coordination with ICE should be arrested, and Brockton Rep. Michelle DuBois sparked an outcry when she warned unauthorized immigrants in her community about rumors that ICE agents would be in the area.

With the swearing-in of Justice Elspeth "Ellie" Cypher on Friday, a majority of the seven high court justices were nominated by Gov. Charlie Baker.

The American Civil Liberties Union of Massachusetts said it knows of no other state supreme court that has heard a case about the legality of ICE detainers, which it deems unlawful.

"The federal government is absolutely right that in our federal system the relationship between the federal and state governments is built on comity, on respect and quite often on cooperation," ACLU of Massachusetts Legal Director Matthew Segal told reporters after the proceeding. "But friends don't ask friends to violate their own constitution."

Segal said there are other legal ways in which state and federal authorities can cooperate, and said, "Here in Massachusetts, law enforcement officers can't arrest somebody just because someone else asked them too, even if that someone else is the federal government."

In an address to Congress in February, Trump said he aimed to "restore integrity" to the nation's immigration system for the benefit of its communities.

"By finally enforcing our immigration laws, we will raise wages, help the unemployed, save billions and billions of dollars, and make our communities safer for everyone," Trump said, according to a transcript. "We want all Americans to succeed, but that can't happen in an environment of lawless chaos. We must restore integrity and the rule of law at our borders."

Segal said advocates around the country have been "fighting these battles" about ICE detainers for years.

Cypher on Tuesday questioned Winger about what the remedy should be if the court ruled that arrests based on detailers are unlawful but some law enforcement declined to comply. Winger replied, "That sounds like a matter of contempt."

The court generally issues written decisions within 130 days of oral arguments.