I like to think I know quite a bit about both Congress and the presidency, but I know I get fuzzy when it comes to specific rules. There's a lot of speculation out there, and I realized I didn't know the answers, so I decided to do a bit of research and write what I hoped would be a definitive post on the subject. However, it turns out the answers are unclear. So I'm going to write up what I learned from looking into it over the last several days, but I'll revisit and revise if I lean more.
Here we go. First, short answers.
Q. What's counts as a recess?
A. The current practice is that a recess within a session of Congress must be at least three days to enable the president to make recess appointments. However, it's not clear whether that practice, from a Clinton-era DOJ statement, is binding or not, nor whether there is in fact any Constitutionally mandated minimum length of recess.
Q. Can the House force the Senate to stay in session, thus preventing recesses longer than three days?
A. No one seems to have any idea at all, but there appears to be a presidential power to force a recess.
Is that uncertain enough?
Okay, now, the details.
1. What counts as a recess?
There are two kinds of recesses: between sessions of Congress, and within sessions of Congress. (I should quote, my emphasis: “[t]he 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.”). The current practice is that for within-session recesses, the break must be three days or more to count for the Constitutional standard. This has been adjudicated, in a 2004 case that reached the Court of Appeals (Evans v. Stephens), in which the 11th Circuit said:
The Constitution, on its face, does not establish a minimum time that an authorized break in the Senate must last to give legal force to the President’s appointment power under the Recess Appointments Clause. And we do not set that limit todayA decade earlier, a Clinton administration DOJ memo stated the three-day-minimum opinion, which as near as I can tell was the first time any specific lower limit has been articulated by the executive branch (or, for that matter, any other branch). It is unlikely in practice that the Obama administration would violate that opinion, which both Clinton and George W. Bush respected, but it seems to me it is entirely unclear what would happen if Obama claimed that, say, a weekend counted as a "recess."
What is worth noting is that the courts have ruled on recess appointments several times, and therefore we could expect any Obama action in this area to be judiciable (although I assume that for a case to go forward it would take someone affected by official acts of the recess appointee; Congress wouldn't have standing to simply challenge the appointment in the first instance. Lawyers, am I correct?). Presumably, judges would rule, if forced, that there is some minimum limit to a in-session recess; if not, presidents could make recess appointments every night after the Senate goes out, thereby circumventing the normal nomination/confirmation process (almost) entirely.
One thing to add: in addition to recesses during Congressional sessions, there are also recesses between sessions; indeed, until the 20th century that was when recess appointments happened, and the legal status of in-session appointments wasn't yet clear.
House Republicans are threatening to keep in session through December in order to prevent any between-session recess appointments. However, the president would have precedent, albeit a contested precedent, on his side. In 1903, Teddy Roosevelt made 160 recess appointments between the first and second sessions of the 58th Congress (here, see 10) even though the second session began immediate after the first session ended (on December 7 at noon). In my view, it is unlikely, although possible that the courts would throw out recess appointments made during a longer, but still very short, recess between sessions.
2. Who wins if the Senate wants a recess and the House doesn't?
At the end of the George W. Bush administration, Democrats in the Senate used an innovative strategy to block recess appointments: they stopped taking recesses. Now, House Republicans are trying to block Obama's recess appointments with the same tactic. The key is the Article I Constitutional rule that neither House of Congress can "adjourn for more than three days" on its own, so if the House doesn't take a recess, then the Senate can't, at least for more than the three days that would allow for appointments under the current interpretation (which, remember, is not necessarily binding).
However, Public Citizen's David Arkush points everyone to an Article II provision, which says that "in Case of Disagreement between them, with Respect to the Time of Adjournment, he may adjourn them to such Time as he shall think proper." Arkush interprets this to mean that if the two Houses disagree on whether to take a recess or not, the president would be able to resolve the dispute.
Is that correct? After asking around a bit, I can't find any answers, including any precedents. As far as I know (and again, I'll revise if I learn any more), this is an unused presidential power...certainly recently. The power does receive one brief mention in Federalist 69 (by Hamilton): "The President can only adjourn the national legislature in the single case of disagreement about the time of adjournment." Hamilton is at pains to show that the president's power is limited, so it's interesting that he doesn't emphasize any potential limitations of the adjournment power; for him, it appears to be, as Arkush has it, simply triggered by disagreements between the House and the Senate.
Now, in the event, it may be unlikely that a president who has been quite hesitant to make recess appointments in general would assert a possibly untested presidential power in order to protect his ability to make those appointments. But that's a different story; we're interested here in what the president can do, not what he may do.
Is it likely that the courts could act to protect the House if the president tried to assert this power? In this instance, unlike the question of a recess appointment during a very short recess, it seems to me that the House would definitely have standing to challenge the president in court. And I do think that it's the sort of thing that the Supremes should legitimately have some say in. As far as what they would say...well, after 2000, I don't like to speculate on that sort of thing.
Additional Sources: CRS FAQ; CRS Legal Overview. I also consulted briefly with Congressional scholar Sarah Binder and presidential scholar Matthew Dickinson, but all responsibility for mistakes here lies with me, not them.