The university's conduct board levied the suspension because of Barber's involvement in a fight at an off-campus party in July.
The terms of the stay prevent Barber from contacting the student he injured, consuming alcohol, using drugs or attending alcohol-related functions.
"We respect today's decision by the Whitman County Superior Court and immediately will reinstate Robert Barber as a student at Washington State University in good academic standing," WSU president Kirk Schulz said Wednesday in a statement. "We look forward to a final decision by the court early next year.
"With his reinstatement as a student, the athletic department will determine Mr. Barber's status as an active member of the Cougar football team."
Bill Moos,the WSU director of athletics, issued a similar statement, adding that Barber's playing status will be determined by coach Mike Leach.
In a statement to ESPN, Leach said, "We're really excited to have [Barber] back. He is a good person and an important part of our team and I applaud the judge's decision."
Barber's attorney, Stephen Graham, argued that WSU's student conduct board destroyed records of questions asked by Barber and an adviser at Barber's conduct board hearing on Sept. 13, and that this prevented the appeals board from later ruling with all the necessary information, according to the Seattle Times.
Barber was initially expelled, but through an appeals process that ruling was reduced to a suspension in October. On Nov. 4, Schulz announced the school would allow Barber to finish his coursework off campus and graduate on time this December.
In seven games this year, Barber, who is from American Samoa, has 11 tackles, 2.5 for loss and two sacks.
No. 22 Washington State (8-2, 7-0 Pac-12) plays at No. 10 Colorado (8-2, 6-1) on Saturday.