CHICAGO – A federal appeals court in Chicago heard arguments Friday in a case that challenges whether President Barack Obama had the authority to appoint three people to the National Labor Relations Board without Senate approval — and who gets to decide whether the Senate is in session.

At issue are three NLRB appointments Obama made in January under a provision for filling vacancies when Congress is in recess.

The Senate had taken a 20-day recess, but Republican leaders and right-to-work groups claimed it technically stayed in session because it was gaveled in and out every few days, and therefore Obama's appointments were unconstitutional. Obama lawyers argue the Senate itself had called for a recess, no business was conducted and attendance wasn't required during the brief "pro forma" sessions.