According to CBA rules, Matt Cooke is no longer considered a repeat offender. Despite his five suspensions, Cooke’s last suspension was March 2011 -- 23 months ago. The rule is your repeat offender status gets cleared after 18 months without infraction.
Now, obviously Brendan Shanahan couldn't possibly ignore Cooke's past if he did something the disciplinary committee ruled was illegal, but the rules state that Cooke is no longer a repeat offender.