As thousands of King Soopers union members are on strike after failed negotiations, the grocery giant filed a lawsuit against the union on Friday.

Union members took to the picket lines Thursday against King Soopers stores across the Denver area and in Boulder and Louisville. Here’s a list of the impacted stores.

Unionized King Soopers workers in Broomfield and Boulder counties joined their peers in the Denver metro area to vote in favor of a strike authorization this week as the Kroger Co.-owned (NYSE: KR) grocery-store chain and the United Food and Commercial Workers Local 7 have failed to agree on terms for a new labor contract.