The Supreme Court delivered a blow Thursday to President Obama, ruling that he went too far in making recess appointments to the National Labor Relations Board.

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In a unanimous decision, the high court sided with Senate Republicans and limited the president's power to fill high-level vacancies with temporary appointments. It was the first-ever Supreme Court test involving the long-standing practice of presidents naming appointees when the Senate is on break.

In this case, Obama had argued that the Senate was on an extended holiday break when he filled slots at the NLRB in 2012. He argued the brief sessions it held every three days were a sham that was intended to prevent him from filling the seats.

The justices rejected that argument, though, declaring the Senate was not actually in a formal recess when Obama acted during that three-day window.

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Justice Stephen Breyer said in his majority opinion that a congressional break has to last at least 10 days to be considered a recess under the Constitution.

"Three days is too short a time to bring a recess within the scope of the Clause. Thus we conclude that the President lacked the power to make the recess appointments here at issue," Breyer wrote.

At the same time, the court upheld the general authority of the president to make recess appointments.

Senate Republican Leader Mitch McConnell, among those who criticized the president for unilaterally filling the NLRB slots, applauded the high court decision on Thursday.

"The president made an unprecedented power grab by placing political allies at a powerful federal agency while the Senate was meeting regularly and without even bothering to wait for its advice and consent," he said in a statement. "A unanimous Supreme Court has rejected this brazen power-grab."

On a separate track, House Speaker John Boehner said a day earlier he plans to proceed with a lawsuit against the president over his alleged abuse of executive power.

Reacting to the Supreme Court decision on Thursday, White House Press Secretary Josh Earnest said the administration is "deeply disappointed" in the ruling. He said that while the administration disagrees with the decision, it will honor it.

The issue of recess appointments receded in importance after the Senate's Democratic majority changed the rules to make it harder for Republicans to block confirmation of most Obama appointees.

But the ruling's impact may be keenly felt by the White House next year if Republicans capture control of the Senate in the November election. The potential importance of the ruling lies in the Senate's ability to block the confirmation of judges and the leaders of independent agencies like the NLRB. A federal law gives the president the power to appoint acting heads of Cabinet-level departments to keep the government running.

Still, the outcome could have been worse for the administration. The justices, by a 5-4 vote, rejected a sweeping lower court ruling against the administration that would have made it virtually impossible for any future president to make recess appointments.

The lower court held that the only recess recognized by the Constitution is the once-a-year break between sessions of Congress. It also said that only vacancies that arise in that recess could be filled. So the high court has left open the possibility that a president, with a compliant Congress, could make recess appointments in the future.

The case decided Thursday arose out of a dispute between the NLRB and a Pepsi-Cola distributor, Noel Canning. The NLRB had ruled against him in a labor dispute, but Canning argued that three of the five board members were improperly appointed.

A recess appointment can last no more than two years. Recess appointees who subsequently won Senate confirmation include Chief Justice Earl Warren and Justice William Brennan, Federal Reserve Chairman Alan Greenspan, two current NLRB members and Consumer Financial Protection Bureau director Richard Cordray. Former UN Ambassador John Bolton is among recess appointees who left office because they could not win a Senate vote.

The Associated Press contributed to this report.