The Player Assistance program is jointly administered by a panel of NHL and NHLPA appointed doctors. It was formerly known as SABH, established in 1996 IIRC—the Substance Abuse and Behavior Health program.
The first principle of the program is if a player has a substance abuse problem, or a mental/behavior health problem, the default action is getting the player into a doctor supervised treatment program—not terminating the player’s contract.
Ideally the Player Assistance program is protecting the player’s contract and salary while they undergo treatment. If a player refuses treatment or violates the doctors’ treatment plan then escalations can happen including suspension without pay and termination of contract.