AUGUSTA — The Maine Department of Health and Human Services will begin enforcing a new rule barring state money from being used to fund General Assistance for undocumented immigrants.

Attorney General Janet Mills and others called the implementation of the rule illegal, saying that DHHS had not followed the process of public comment and legal review required to change General Assistance eligibility requirements.

DHHS originally proposed a sweeping rule change that would have prevented state money — which accounts for 50 to 90 percent of General Assistance funds, depending on the town — from being used to assist all immigrants and asylum seekers. That proposal was subject to public comment and hearings, and it was screened by the attorney general’s office.

The attorney general’s office said that rule change was illegal because it represented an unfunded mandate on towns and cities, exceeded the authority of DHHS and violated the Constitution.

In response, Department of Health and Human Services Commissioner Mary Mayhew said in a news release that she would amend the rule change to limit only the issuance of General Assistance to “illegal immigrants.”

Mills on Wednesday said her office had not seen or approved any new rule and that DHHS was attempting to create law with press releases.

“They haven’t asked us for any guidance,” she said. “From the reading of the press release, it sounds like a very political act, and an end run around the Constitution. This would have significant practical and legal issues.”

Those issues include how clerks should determine which immigrants are “illegal” — which most municipal clerks are not trained to do — and how the department intends to define the population they’re looking to exclude from receiving state funds. Mills also doubted the claim by DHHS that the rule change will save the state $1 million.

“I don’t believe there’s any statutory authority for them to do what they’re doing,” she said. “The appropriate thing to do would be to respect there are three branches of government, not one. Assuming there’s merit to the idea, put it to the Legislature, put it to public hearing, to debate and discussion with full transparency. … Instead, they wait until the Legislature’s gone and do something by press release.”

The American Civil Liberties Union of Maine, which opposed the initial proposed rule change, called the action by DHHS “shocking.”

Zachary Heiden, ACLU of Maine’s legal director, pointed to Maine’s Administrative Procedures Act and said the department simply had bypassed the legal process required to implement a change in General Assistance eligibility requirements.

“This rule is illegal. It can’t go into effect. The department or agency simply has no authority to create a rule outside this process,” he said. “I’ve never seen something so flagrant.”

In a press release, Mayhew said the rule change will bring Maine into compliance with federal law.

“Federal law clearly points out that unless a state has adopted and approved a statute that allows for this benefit to be provided to these populations, it is against federal law to provide them,” she said. “Maine does not have any provision in state statute that grants such a provision.”

DHHS will send notifications of the rule change to municipalities this week and begin enforcing the new rule shortly thereafter, according to a news release from the department.

Heiden said he hopes municipalities will ignore the notifications until the agency goes through the proper process. If not, he said, it’s possible that someone affected by the new rule — whether that’s a General Assistance applicant subjected to it or a municipal clerk made to enforce it — could file a lawsuit.

If that happens, he said, the ACLU may get involved.

“We opposed this rule when it went through the process the first time, and we’ll do so again if the DHHS comes to its senses and goes through the process again,” he said. “If they’re not going to follow the rules, we’ll have to think about other options.”