LANSING, Mich. – The Michigan Supreme Court on Friday struck down months of orders by Gov. Gretchen Whitmer that were aimed at preventing the spread of the coronavirus, saying she drew authority from a 1945 law that is unconstitutional.

The decision is an extraordinary development in a monthslong conflict between Whitmer, a Democrat, and the Republicans who control the Legislature and have complained that they’ve been shut out of major orders that have restricted education, the economy and health care.

Coincidentally, the court’s opinion emerged on the same day that Whitmer’s critics submitted more than 539,000 signatures in a bid to repeal the 1945 law.

The governor said the 4-3 decision, with Republican-nominated justices in the majority, was “deeply disappointing.” But Whitmer didn’t signal that she was giving up. She said her emergency declaration and related orders still can remain in place for 21 days, and then many of them will continue “under alternative sources” of law.

Whitmer didn’t elaborate, but it’s likely that her administration will act under public health statutes.

“Every state and the federal government have some form of declared emergency,” she said. “With this decision, Michigan will become the sole outlier at a time when the Upper Peninsula is experiencing rates of COVID infection not seen in our state since April.”

For nearly seven months, Whitmer has imposed — and sometimes eased — restrictions on Michigan’s economy, K-12 school system, health care and even visits to state parks, all in an attempt to reduce the risk of the highly contagious virus, which has infected 126,000 residents and killed more than 6,700.

Masks are required in enclosed public spaces and in crowded outdoor places. Restaurant capacity is limited to 50%. People must work remotely if they can, and indoor residential gatherings are capped at no more than 10 people.

Republican officials said Whitmer should have continued to use a 1976 law, which gives lawmakers a say in any emergency declarations after 28 days.

The Supreme Court said the ’45 public safety law cited by Whitmer granted Michigan governors unchecked authority.

“That act is an unlawful delegation of legislative power to the executive branch in violation of the Michigan Constitution,” Justice Stephen Markman wrote. “Accordingly, the executive orders issued by the governor in response to the COVID-19 pandemic now lack any basis under Michigan law.”

In a dissent, Chief Justice Bridget McCormack said she would have let the law stand, even if it gives a governor sole authority to “exercise the whole of the state’s police power in some emergencies.”Lawmakers could repeal the law or amend it, and frustrated residents could sue if they don’t agree with specific orders, McCormack said.

“The majority needlessly inserts the court into what has become an emotionally charged political dispute,” McCormack wrote, joined by justices Richard Bernstein and Megan Cavanagh.

Although the constitutionality of the ’45 law produced a split ruling, the justices unanimously agreed that any orders past April 30 without input from the Legislature were not valid.

The case reached the Supreme Court in an uncommon way. A federal judge overseeing a lawsuit that makes state and federal claims about Whitmer’s powers asked for an opinion on the constitutionality of the Michigan laws.

“Our Constitution matters, and this was a big win for our democratic process,” said Republican House Speaker Lee Chatfield of Emmet County.

In a footnote to his opinion, Markman offered an optimistic message.

“Our decision leaves open many avenues for the governor and Legislature to work together to address this challenge and we hope that this will take place,” he said.