https://www.siliconvalley.com/2019/09/06/us-launches-antitrust-probe-of-automakers-deal-with-california/

WASHINGTON – The U.S. Justice Department is investigating whether the decision of four automakers in July to reach a voluntary agreement with California to adopt state emissions standards violated antitrust law, people briefed on the matter said on Friday.

The antitrust division has sent a letter to the automakers indicating the Justice Department had opened a preliminary inquiry, the people said, and comes as the Trump administration has ramped up its opposition to automakers seeking to sidestep it on rolling back Obama-era fuel efficiency rules.