Scott Pruitt said he wouldn't accept legal donations from lobbyists or companies that might do business with the EPA.
Pruitt reportedly asked his staff to come up with official reasons for the trips.
EPA Administrator Scott Pruitt's trip to Morocco was initially reported to have cost about $40,000.
The Trump administration has challenged an Obama-era policy that requires car manufacturers to roughly double fuel efficiency in the coming years.
Gov. Jerry Brown and Attorney General Xavier Becerra announced the lawsuit Tuesday.
Specifically, the inspector general confirmed to lawmakers it was looking into Pruitt's $50-a-night apartment rental from a lobbyist couple.
The Environmental Protection Agency said in October it might roll back the Clean Power Plan. The public comment period ends Tuesday.
Pruitt is under numerous investigations into his actions, including multiple inquiries from both the EPA itself and the White House.
EPA chief Scott Pruitt has a new proposal that could change how the agency conducts a lot of its research.
EPA head Scott Pruitt said such a rule would increase the agency's transparency, but critics say it could ban valuable data from consideration.
President Donald Trump said EPA Administrator Scott Pruitt's security costs are "somewhat" more expensive than his predecessors. They're a lot more.
This will reportedly make six separate investigations into Pruitt's activity. And that's just from the EPA inspector general's office.