Walmart Stores unlawfully retaliated against workers who participated in strikes in 2013 and must offer to reinstate 16 dismissed employees, a National Labor Relations Board judge has ruled.

Administrative Law Judge Geoffrey Carter said in a ruling posted on the board’s website on Thursday that Walmart violated labor laws by “disciplining or discharging several associates because they were absent from work while on strike.”

Most of the decision is related to a coordinated set of strikes at various Walmart stores in May and June of 2013. Judge Carter was ruling on a complaint filed by the labor agency on behalf of a union-backed worker group, OUR Walmart, in 2014.

Walmart can appeal the decision to the agency’s board in Washington.

“We disagree with the administrative law judge’s recommended findings and we will pursue all of our options to defend the company, because we believe our actions were legal and justified,” said a spokesman for Walmart, Kory Lundberg.