WASHINGTON (Reuters) - Supreme Court justices, hearing a dispute over presidential powers a day before the U.S. election, indicated on Monday they might curb a president’s authority to staff top administration posts in a case involving the National Labor Relations Board.

U.S. Supreme Court is seen in Washington, U.S., October 3, 2016. REUTERS/Yuri Gripas/File Photo

The eight justices heard an hour-long argument in a 2014 legal challenge brought by Arizona-based private ambulance company SW General Inc to President Barack Obama’s temporary appointment of Lafe Solomon in 2011 as NLRB general counsel. Obama also nominated Solomon to fill the position permanently, a move that required U.S. Senate approval.

The company, a subsidiary of Envision Healthcare Holdings Inc, challenged Solomon’s appointment after the labor board found SW General had committed an unfair labor practice by discontinuing bonus payments for long-term employees.

If SW General wins, the NLRB order would be thrown out because of Solomon’s participation.

Solomon filled in for former general counsel Ronald Meisburg, who resigned in 2010. Obama withdrew Solomon’s nomination after it stalled for more than two years. The Senate ultimately confirmed Richard Griffin to the post in 2013.

SW General argued that Solomon should not have continued to fill the position on a temporary or “acting” basis pending Senate confirmation.

In a 2015 ruling against the administration, the U.S. Court of Appeals for the District of Columbia Circuit said a 1998 federal law bars officials from serving in an acting role while awaiting Senate confirmation unless they were previously the “first assistant” to that post.

The administration contends others who fill posts temporarily can also be nominated, including those previously confirmed by the Senate to another position.

The Supreme Court in 2014 limited presidential powers in another case involving the NLRB, ruling that three 2013 appointments Obama made to the board while Congress was in recess were invalid.

Justice Anthony Kennedy questioned whether new constraints on presidential appointment power would make as much of a practical difference as Obama’s administration claims, calling the system “quite capable of accommodating” a ruling in favoring SW General.

Justice Ruth Bader Ginsburg said concerns about past government actions taken by acting officials being challenged retroactively were overblown.

The administration said 100 appointments over the past 18 years would have been invalid under the approach sought by the company, including several in sensitive national security jobs.

Justice Elena Kagan said with the recent history of “partisan bickering” over appointments, “we would have heard about it” if members of Congress had objected in the manner the company does.

The outcome of the case could assume added importance if the next president faces protracted nomination battles and opts to appoint officials on a temporary basis.

A ruling is due by the end of June.