The Supreme Court on Monday agreed to hear a case that, at its heart, is a question of semantics: When is a Senate recess actually a Senate recess? Stemming from a January 2012 Obama appointment of three officials to the National Labor Relations Board, the case of NLRB v. Noel Canning could now to stand to jeopardize months of work by the agency — and potentially many other administrative decisions of the distant past and uncertain future.

The Constitution gives the president the ability to make appointments without Senate approval when the Senate is out of session. The goal is obvious: If the Senate were on an extended break and the president needed a Secretary of Defense, for example, Article II, Section 2 gives the president the ability to name one. It reads:

The President shall have Power to fill up all Vacancies that may happen during the Recess of the Senate, by granting Commissions which shall expire at the End of their next Session.

Pretty straightforward. Except that how and when Congress is on recess can be surprisingly subjective.

In January of last year, despite most members being out of town, the House held "pro forma" sessions during which one or two members would appear on the floor every few days to quickly open and close business. Even though no business was conducted, Republican members meant to meet the minimum standard to keep an official recess from beginning. (This was a tactic developed by Democratic senators in 2007.) During one of the short breaks during that period, the president, frustrated, made the NLRB appointments after arguing that the Congress was in recess.

This January, the D.C. District Court of Appeals threw those appointments out, arguing, in the words of one judge, that allowing the president to decide when Senate was in recess "would demolish the checks and balances inherent in the advice-and-consent requirement." But two of the three-judge appeals court's members went further than simply stating that the pro forma sessions were enough to block the president's constitutional authority. Instead, as The New York Times reported, they asserted that any intrasession recess appointment was invalid. In other words, that the only point at which Article II, Section 2 applied was after the Senate had adjourned a session and before it had begun another one. This upends centuries of precedent, and could have significant reverberations for recent administrations.

Nearly all [appointments under Obama, Bush, and Clinton] would be unconstitutional under the rationale of the United States Court of Appeals for the District of Columbia Circuit. It ruled that presidents may bypass the confirmation process only during the sort of recess that occurs between formal sessions of Congress, a gap that generally arises just once a year and sometimes is skipped, rather than other breaks throughout the year. Two of the three judges on the panel also ruled that presidents may fill only vacancies that arise during that same recess.

That comprises some 342 appointments — far more than the three NLRB appointments originally at issue. In April, the administration asked the Supreme Court to consider the case; today, it agreed to do so. It will consider not only the broader question of intrasession appointments, but also those conducted during pro forma breaks.

Multiple attorneys general have written in support of the constitutionality of intrasession recess appointments, including Harry Daugherty in 1921 and a current assistant AG.

The decision, which could have massive repercussions for administrative decision-making, stems from a rather mundane dispute. Noel Canning, a Pepsi distributor in Washington state, sued the NLRB after the board ruled that the company had committed an unfair labor practice. If the pro forma session argument is upheld, the NLRB will not have had a quorum to make any decisions since January of 2012, since three of its members would never have been appointed. The anti-labor National Right to Work Foundation outlines hundreds of subsequent decisions involving those members, all of which might be at risk.

If, however, the Supreme Court invalidates all previous intrasession appointments, the repercussions are almost incalculable. The power of the Constitution, as always, lies in its interpretation.