Saints boss Alan Gaffney suggested after the 34-25 defeat on March 3 that the 25-year-old - whose contract expires at the end of the season - had not wanted to play for the club.
The club have now released a statement on the matter in which they confirmed that North will be available for selection for the final five matches of the campaign having returned from international duty.
"Following a meeting with the club on Monday, George North accepted responsibility for missing a training session ahead of Saints' Aviva Premiership clash with Sale Sharks earlier this month, and has been disciplined internally," the statement read.
"North, who returned to training on Monday, will be available for selection for Saints' five remaining matches this season, starting with this weekend's clash against Newcastle Falcons."
The game between Northampton and Sale came during a break in the Six Nations fixture schedule, with George able to play for his club during the tournament's fallow weeks.