Gov. Charlie Baker is being challenged in the state's highest court for his decision to shut down businesses he deemed non-essential when the pandemic hit Massachusetts.

"He's turned the government upside down. I mean, at this point, the legislature is left to approve or disapprove of the governor's policy choices. That's not how it's supposed to work," Michael DeGrandis, an attorney for a group of local businesses and national conservative interests that say Baker overstepped his office, said Friday as the Supreme Judicial court heard oral argument in the case.

Baker argues he has the authority to make shut down decisions to prevent public harm under the state's Civil Defence Act.

"The executive orders and the ability to execute and follow through on those executive orders was an incredibly important part of the success the Commonwealth has had in beating back and fighting COVID," Baker said Thursday at an event in Medford about sustaining businesses harmed by the pandemic.

The heart of the court argument is whether a global pandemic like COVID-19 is a natural disaster similar to earthquakes or other acts of God as laid out in the law.

"The governor's argument that there is some lesser rights available to people during times pandemic is simply wrong," Degrandis said.

If the court reject's Baker's authority, it could force lawmakers to change the law before another shutdown is necessary.