Gov. Tim Walz had the legal authority to mandate face masks when he declared a public health emergency in the early days of the COVID-19 pandemic, the Minnesota Court of Appeals ruled Monday.

Walz declared a peacetime emergency in March 2020 and mandated masking in most indoor public spaces in July 2020. The conservative Upper Midwest Law Center sued, challenging the mask requirement as unconstitutional. Walz lifted the mandate in May 2021, at which point the Court of Appeals declared the case moot.

But the Minnesota Supreme Court in February sent the case back to the appeals court to settle the key legal question behind the case: whether the Minnesota Emergency Management Act of 1996 authorizes a governor to declare a peacetime emergency during a public health emergency such as the pandemic. The high court called it an “important issue of statewide significance.”

The appeals court rejected as “unreasonable” the plaintiffs’ assertions that the coronavirus “most likely” originated from a laboratory leak, so that the resulting pandemic did not occur “naturally” and therefore was not an “act of nature” under the state law.

The appeals court used similar legal reasoning earlier this year when it rejected arguments by a woman who had been convicted of operating a wine bar and restaurant in Albert Lea in violation of the governor’s pandemic orders.