California Gov. Gavin Newsom had attacked the DOJ inquiry as politically motivated and part of a pattern in President Donald Trump's feud with the state over environmental rules and other issues.

“These trumped up charges were always a sham — a blatant attempt by the Trump administration to prevent more automakers from joining California and agreeing to stronger emissions standards," Newsom said in a statement Friday. "This is a big loss for the President and his weaponization of federal agencies — and a victory for anyone who cares about the rule of law and clean air.”

In addition to the antitrust probe, Trump's agencies have also threatened to take away California's highway funding, sued over the state's cross-border climate pact with Quebec and accused San Francisco of letting homeless people's waste cause water pollution. On the other coast, the Department of Homeland Security this week barred New York residents from enrolling in federal programs that allow vetted travelers to breeze through airport lines, blaming a new state law granting driver’s licenses to undocumented immigrants.

The end of the antitrust probe came as the Trump administration is preparing to finish rolling back planned increases in federal fuel-economy standards and as it defends in court its decision to strip California's long-standing ability to set its own requirements.

The latter action threatens to fracture the auto market, as 13 states plus the District of Columbia follow California's standard, representing 40 percent of vehicle sales. California has asserted a right to set stronger marks due to its unique topography and persistent local air pollution problems.

Leah Nylen contributed to this report.