A three-judge panel of the US Court of Appeals for the First Circuit Tuesday overturned a ban prohibiting US immigration authorities from arresting undocumented immigrants at courthouses in Massachusetts.

In 2018, US Immigration and Customs Enforcement (ICE) formalized a policy of attempting to arrest undocumented immigrants when they appeared at state courthouses for judicial proceedings. Two Massachusetts district attorneys, the public defender’s office and a non-profit immigrant advocacy organization filed a lawsuit against ICE and asked for a preliminary injunction against the practice. They claimed that ICE was in violation of the Immigration and Nationality Act (INA) and lacked authority to make civil arrests at courts. The district court agreed, and granted an injunction last year.

At issue is a claim that the INA implicitly incorporates a common law privilege that protects those attending court from being subject to civil arrest. While nothing in the text of the INA prohibits these types of courthouse arrests, the plaintiffs argued that the law must be read in light of the nonderogation canon, a method of statutory construction that holds that courts must assume Congress is aware of long-standing common law principles and, absent express language to the contrary, intends to keep them.

Judge Bruce Selya wrote Tuesday that “the nonderogation canon does not give courts carte blanche to read a grab bag of common law rules into federal statutes simply to effectuate what those courts may perceive as good policy.” The circuit court held that the nonderogation canon applies if the facts of the common law rule and the statute in question are sufficiently analogous. The common law prohibited civil arrests at court by private litigants, while here the arrests are being carried out by a government agency. The panel vacated the preliminary injunction and remanded the matter back to the district court.

Rachael Rollins, district attorney for Suffolk County and one of the plaintiffs in the case, said in a statement that “this fight is far from over” and that the plaintiffs “are absolutely on the right side of justice here.”