The president's appointments showed pro-union bias, according to congressional Republicans. (Creative Commons)

The ruling is a reprimand for the president and a victory for House Republicans.

Obama made three appointments to the National Labor Relations Board on Jan. 4, 2012, while the Senate was on an unofficial 20-day recess. 

GOP legislators claim they were still officially in session, due to technical "pro forma" sessions which entail "gaveling in and out." 

The NLRB appointments were made despite months of objections from Senate Republicans, who allege Obama's appointments were made with a pro-union bias.

According to the Daily Beast, "The decision could invalidate all the decisions made by the NLRB since then—and could raise questions about Obama’s nomination of Richard Cordray to the Consumer Financial Protection Bureau."

Republican House Speaker John Boehner called the court's ruling "a victory for accountability in government," according to The Associated Press. 

White House Counsel Kathryn Ruemmler maintained that Obama's actions were constitutional. "The mere fact that the Senate has stated it is in a 'pro forma' session at which no business shall be conducted does not change the fact the Senate is unable to perform its constitutional role in the confirmation process," she told CNN. 

Presidential recess appointments have become increasingly common in recent decades as a method of bypassing Senate objections. George W. Bush used an official recess as an opportunity to fill a judgeship. 

It's likely today's finding will curtail the practice in the future.

For more on the impact of today's ruling, go here. Read other Neon Tommy stories on the Senate here.

Reach Executive Producer Lauren Madow here. Follow her here.