Is that enough to terminate his contract?
On top of what Stimpy says there, even closer from home there is the Standard Player's Contract (Exhibit 1 of the CBA):
2 The Player further agrees
(e) to conduct himself on and off the rink according to the highest standards of
honesty, morality, fair play and sportsmanship, and to refrain from conduct detrimental to the best interest of the Club, the League or professional hockey generally.
and
14. The Club may also terminate this SPC upon written notice to the Player (but only after
obtaining Waivers from all other Clubs) if the Player shall at any time:
(a) fail, refuse, or neglect to obey the Club's rules governing training and conduct of
Players, if such failure, refusal or neglect should constitute a material breach of this SPC.
(b) fail, refuse or neglect to render his services hereunder or in any other manner
materially breach this SPC.
In the event of termination under Paragraph 14(a) or (b) the Player shall only be entitled
to compensation due to him to the earlier of the date such notice is personally delivered to him or the date such notice is e-mailed to him.
In the event this SPC is terminated by the Club while the Player is "away" with the Club
for the purpose of playing games the installment then falling due shall be paid on the first weekday after the return "home" of the Club.
But I don't know if there's some substance abuse protocols and treatment that NHLPA might insist to be done instead of termination in case of plain drug use.