Gov. Tim Walz acted within his authority by mandating face masks after declaring a public-health emergency during the COVID-19 pandemic, the state Court of Appeals ruled Monday.

Walz declared a peacetime emergency in March 2020 and implemented the mask requirement for most indoor public spaces in July 2020.

The appellate court sought to answer a single question: Does the Minnesota Emergency Management Act of 1996 authorize the declaration of a peacetime emergency based on a public-health crisis such as the COVID-19 pandemic?

An opinion written by Judge Michelle Larkin for a three-judge panel that also included Judge Kevin Ross and senior Judge Roger Klaphake said the court found Walz acted appropriately.

The Upper Midwest Law Center challenged the mask requirement as an unconstitutional infringement on residents' rights. On behalf of a group of plaintiffs, the center claimed Walz's declaration of a peacetime emergency during the pandemic exceeded his powers.

The case started in Ramsey County where Judge John Guthmann sided with Walz and dismissed the case. The plaintiffs appealed to the state Supreme Court and the matter landed back at the Court of Appeals.

Walz lifted the mask mandate in May 2021, but the court still sought to answer the question.

The court noted that the 1996 Minnesota Emergency Management Act grants the governor certain "emergency and disaster powers" to address "natural and other disasters of major size and destructiveness."

The plaintiffs challenged the law primarily on the grounds that COVID-19 was not an "act of nature" because the pandemic "most likely" originated from a lab leak and therefore the pandemic did not occur naturally, according to the opinion.

But the court found that interpretation unreasonable. Requiring the court "to identify whether any human action had contributed at all to naturally occurring forces or events could prove impossible to resolve," the opinion said.

The court noted that other situations allowing the governor to declare a peacetime emergency result from human activity, including "a technological failure or malfunction, a terrorist incident, an industrial accident, a hazardous materials accident, or a civil disturbance."

In a statement, a Walz spokeswoman said, "We are pleased that the courts have once again affirmed that the governor's emergency actions during the pandemic were lawful."

The Upper Midwest Law Center did not return a message seeking comment. The center describes its goal as limiting "governmental special interest and public union overreach."