CHICAGO (AP) — The Federal Highway Administration has abandoned its appeal of a court ruling against the proposed Illiana Expressway.

Thursday’s motion added to the mounting obstacles in the way of the controversial 47-mile tollway to link Illinois and Indiana south of Chicago.

The agency gave no explanation for dropping its appeal of a federal judge’s ruling in June. That ruling found the U.S. government’s approval of the $1.5 billion project was “arbitrary and capricious” and in violation of U.S. environmental law.

It was in response to a lawsuit filed by Illinois environmental groups contending that federal approval relied on faulty information and didn’t adequately consider environmental impacts.

In his first act after taking office, Illinois Gov. Bruce Rauner suspended the project and others as part of a review of spending.