The Trump administration has closed an antitrust investigation into four automakers that struck a deal with California to follow the state’s stricter tailpipe emissions limits instead of weaker federal standards.

Democrats had suggested the investigation was politically motivated retaliation to deter other companies from following.

The Justice Department closed its investigation into the four automakers, a spokeswoman for Ford Motor Company confirmed Friday afternoon.

Ford, along with BMW, Honda, and Volkswagen, announced last year they would partner with California on fuel economy standards, agreeing to follow limits closer in stringency to the Obama-era limits the Trump administration was seeking to roll back. The deal worsened tensions between the White House and California policymakers, who have vigorously fought the Trump administration’s efforts to scrap or weaken Obama-era climate regulations.

Just a few months after that deal was announced, the Justice Department said it would explore whether the deal violated federal competition laws.

California Gov. Gavin Newsom, a Democrat, declared the dropped investigation a “big loss for the president and his weaponization of federal agencies.”

“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.

The fuel economy limits are a particular pressure point because California long had a special ability under the Clean Air Act to set its own greenhouse gas limits for passenger cars stricter than federal levels. The Trump administration in September eliminated that authority, a step California and more than a dozen other states are challenging in court.

Several auto companies, however, including General Motors, Fiat Chrysler, and Toyota, are backing the Trump administration in that lawsuit.

The Trump administration proposed last year to freeze fuel economy and tailpipe greenhouse gas limits at 2020 levels, a significant step down from the Obama-era rules. A final version of its plans, expected to require only a slight year-over-year increase in fuel efficiency, is currently under review at the White House budget office.