The U.S. Supreme Court on Monday heard oral arguments in a case that could invalidate hundreds of National Labor Relations Board rulings and set the agency back more than a year in its workload if it loses.

The dispute could also determine when presidents can use so-called “recess appointments” to fill key positions that generally require Senate approval, creating serious implications for the White House.

The case, NLRB v. Noel Canning, challenges a D.C. Circuit Court of Appeals decision early last year that said the president’s 2012 board appointments, which occurred while the Senate was on break, were unconstitutional. Hundreds of NLRB rulings involving those panel members are now at stake.

How did this happen?

During Senate breaks, the president has the authority to make “recess appointments,” but Republicans in 2012 were holding pro forma sessions every three days to keep that from happening. For what it’s worth, Democrats and Republicans have both used that tactic when the opposite party controlled the White House.

The Constitution does not specify how many days the Senate has to be away before a president can make a recess appointment, but Republicans argue that none have taken such action during a break of less than 10 days.

Democrats last year made the confirmation process easier by changing Senate rules to prevent the filibusters that have allowed the minority party to block certain types of nominees. Nonetheless, pro forma sessions will remain as a potential barrier if the Supreme Court determines Obama’s recess appointments were invalid, keeping the door open for more conflicts when one party controls the Senate and the other holds the presidency.

Cases in limbo

The Supreme Court’s ruling will determine whether the NLRB has to revisit hundreds of labor disputes that were decided under the board members in question. That leaves scores of workers and their employers in limbo.

Keep in mind that the board’s composition has changed since the NLRB rulings in question took place. Although the panel still leans Democratic, there is no guarantee that its decisions would be the same in each case.

The Senate approved a full slate of board members in July, confirming Harry Johnson III, Philip Miscimarra, Nancy Schiffer, Kent Hirozawa and Mark Pearce. The decisions by that panel are valid in the sense that they do not involve questions about the legitimacy of its members.

The NLRB decided after the lower-court decision in January 2013 that it would move forward with business as usual, issuing more decisions with the controversial board members in place. Critics have questioned that decision, saying the NLRB only added to the potential backlog it would face if it loses its appeal in the high court.

“Regardless of whether you’re in the business community or organized labor, you want to know that the agency is operating with legal authority,” said Steven Bernstein, a labor lawyer who represents employers. “You want to get it right the first time and make the results stick so you don’t face the possibility of waking up and doing it all over again.”

Labor groups largely agreed that the ruling would create difficulties for the NLRB as it tried to move forward. “Each day that Noel Canning remains on the books means further chaos and disarray at the NLRB and difficulties in enforcing workers’ rights,” the AFL-CIO said in a statement last year.

The union’s general counsel could not be reached for comment on Monday.

NLRB spokesman Greg King said on Monday that the agency does not comment on ongoing litigation.

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