Solicitor General Donald Verrilli Jr. warned the court that it would essentially write the recess appointment power out of the Constitution if it found that those appointments were illegal.
The court battle between the Obama administration and Senate Republicans is an outgrowth of the increasing partisanship and political stalemate that have been hallmarks of Washington over the past 20 years, and especially since Obama took office in 2009.
Indeed, Justice Elena Kagan seized on the political dispute to make the point to Verrilli that "congressional intransigence" to Obama nominees may not be enough to win the court fight.
Kagan, Verrilli's predecessor as Obama's top Supreme Court lawyer, suggested that it "is the Senate's role to determine whether they're in recess."
There are three questions before the court — whether recess appointments can be made only during the once-a-year break between sessions of Congress, whether the vacancy must occur while the Senate is away in order to be filled during the same break and whether brief, pro forma sessions of the Senate, held every few days to break up a longer Senate hiatus, can prevent the president from making recess appointments.
Kagan's question addressed the latter point and offers the court a narrower way to rule on recess appointments.
Verrilli seemed to signal he would rather lose on that question than the first two. But under any circumstance he said, "You really are writing the recess appointments power out of the Constitution," he said.
The importance of recess appointments has dimmed in recent months, since majority Democrats changed the Senate's rules to make it harder for the minority party to block the president's nominees to federal agencies and the courts.
But the issue could once again be front and center when the White House and Senate are controlled by different parties.
Senate Republicans' refusal to allow votes for nominees to the NLRB and the new Consumer Financial Protection Bureau led Obama to make the temporary, or recess, appointments in January 2012.
Three federal appeals courts have said Obama overstepped his authority because the Senate was not in recess when he acted. The Supreme Court case involves a dispute between a Washington state bottling company and a local Teamsters union in which the NLRB sided with the union. The U.S. Circuit Court of Appeals for the District of Columbia overturned the board's ruling, and hundreds more NLRB rulings could be voided if the Supreme Court upholds the appeals court decision.
Three federal appeals courts have upheld recess appointments in previous administrations.
Verrilli told the court in written arguments that 14 presidents have temporarily installed 600 civilians and thousands of military officers in positions that were vacant when the Senate went into recess at any point, a practice that has been well-understood by both presidents and lawmakers. A high court ruling that a recess only happens once a year would "dramatically upset that long-settled equilibrium," Verrilli said.
Highlighting the new rules, the Senate was scheduled to vote a few hours after the Supreme Court argument on the nomination of one of those previously blocked Obama appointees, U.S. District Judge Robert Wilkins, to serve on the federal appeals court in Washington.