This is the flight link to the plane that a drunk ran up to and slapped after it landed in PHX.
Which airlines employ strategies to limit the consumption of liquor within the flight? 
All of them.
Your question is kind of irrelevant since in this case the “drunk” was a mentally disturbed homeless guy that jumped over the airport fence and ran up to the plane as it was taxiing. Hardly a lapse in Southwest’s efforts to police it’s own aircraft security I think.