The court ruled 7-0 to uphold a B.C. Court of Appeals ruling that ordered a new trial for the two.
Timothy and Matthew Maybin were charged with manslaughter after a Michael Brophy died following a bar fight.
At trial in 2008, a judge found that they left the victim unconscious on a pool table.
However, because a third man, the bar bouncer, then struck the victim, the judge found there was no way to say who delivered the fatal blow and acquitted the brothers and the bouncer.
The appeal judges overturned the acquittal and ordered a new trial, a ruling which the brothers appealed to the Supreme Court.