The case before the high court, NLRB v. Noel Canning, centers on Obama's Jan. 4, 2012, board appointments of Democrats Sharon Block and Richard Griffin and Republican Terence Flynn. At that time, the Senate was in a recess that began on Dec. 17, 2011. It then held, periodically, brief pro forma sessions until it came back into session on Jan. 23, 2012.

BREYER

Two key issues in the case were the Constitution's Recess Appointments Clause, which permits a president "to fill up all Vacancies that may happen during the Recess of the Senate," and what constitutes a Senate recess. Justice Stephen Breyer, writing for the court majority, noted that the appointments came while the Senate was on a three-day break between pro forma sessions. He said, "Three days is too short a time to bring a recess within the scope of the [Recess Appointments] Clause."

SCALIA

In a separate opinion, Justice Antonin Scalia concurred that Obama had exceeded his authority but said the court majority's limited finding would have serious, negative consequences. Writing for himself and three other justices, Scalia said, "The majority replaces the Constitution's text with a new set of judge-made rules to govern recess appointments." He added, "The majority's methodology … all but guarantees the continuing aggrandizement of the Executive Branch."

As a prime federal arbiter of labor issues, the NLRB also sits at the center of disputes between businesses and organized labor. For years, the board, which is split between Democrats and Republicans, has been the focus of fierce partisan debate. The party holding the White House can name three members.

AFL-CIO President Richard Trumka said Obama "did the right thing and acted on solid legal authority" in making the 2012 appointments.

ABC, which led an industry coalition that filed a brief in support of the case, hailed the ruling. Geoff Burr, ABC vice president of government affairs, said the decision "is a victory for ABC, the Constitution and our system of checks and balances, and it serves as a clear rejection of the president's unprecedented expansion of executive authority."