In a narrow ruling that preserves much of the presidential recess appointment power, the Supreme Court struck down President Obama's 2012 recess appointments to the National Labor Relations Board. The court was unanimous in its judgement for Noel Canning, who challenged the president's decision to fill vacancies on the NLRB, even though the Senate was holding "pro forma" sessions to prevent the president from using that power.
However, the court did affirm that the president is allowed to fill vacancies during intra- and inter-session breaks, as long as those breaks are long enough. And, the Supreme Court ruled that those vacancies may open up either before or during a recess in the Senate. Both of those questions were challenged in a kind of astonishing ruling from the D.C. Circuit, which — as MSNBC explained — held that the president could only use his recess power between sessions of Congress (and not during short breaks), and only if a vacancy opened up during that recess.
The recess appointment power has a long tradition of being used by both parties to work around a Senate in opposition to the president. With today's ruling, the president may only make recess appointments after the Senate has determined it is in recess, and not, as happened with the NLRB appointments, when the president decides that the Senate is in recess. In other words, the President retains the broad scope of his or her recess appointment powers as it has been historically used until this case, and Congress retains its ability to keep itself open for business (even on paper only) to block the president from using that power.