Philadelphia City Hall
CNN  — 

The City of Philadelphia was sued Saturday by a group of business owners and residents alleging its upcoming mask mandate is illegal, court documents show.

Philadelphia is the first major US city to reinstate its indoor mask mandate, which went into effect last week, with enforcement beginning today.

The new mandate comes as the city announced Level 2 Covid-19 response levels, which were triggered when the city saw an increase in confirmed Covid-19 cases more than 50% than the previous 10 days.

Level 2 precautions mean masks are required in all public indoor spaces in Philadelphia, including schools, businesses and restaurants. Businesses can stay mask-free if they require everyone to provide proof of vaccination.

The city’s Public Health Department issued the mandate by emergency order April 11.

The group filing the lawsuit says the mandate violates the state’s Constitution and flouts guidelines established by the US Centers for Disease Control and Prevention (CDC).

“The regulations imposed by Philadelphia are arbitrary and capricious,” the attorney representing petitioners, Thomas W. King III told CNN in an interview Sunday. “Philadelphia jettisoned the CDC regulations and is inventing its own. Philadelphia violated the Pennsylvania Constitution. Things that apply in Philadelphia must apply statewide, but that’s not what’s happening.”

The lawsuit alleges Philadelphia’s Health Commissioner, Dr. Cheryl Bettigole, usurped the General Assembly’s authority by issuing the emergency order. And the CDC currently has no mask mandate in place.

CNN reached out to Philadelphia Mayor Jim Kenney’s office and the city’s Health Department for comment but has not heard back.