This came up during a discussion I was having with a friend who works as head of HR for a medium sized organization, about 600 employees in total. Recently they had to let someone go for poor performance. There was also a suspicion that the employee was showing up to work still intoxicated. Rather than documenting the poor performance and work through the performance improvement steps, they opted to breathalyze the employee when he arrived for work. The employee failed the test, blowing just under the legal driving limit, and was promptly dismissed.

Obviously, this person deserved to be fired, and in America most states have "at-will" employment, meaning you can fire someone for pretty much whatever reason you want, provided it is not an illegal reason. But this got us wondering – could an employer ever bar an employee from consuming alcohol outside work? Would this sort of thing be justifiable? I know several public sectors have random screenings, e.g. for drugs, alcohol and even cheek swabs for tobacco to catch people lying related to their health insurance.

Could an employer institute a rule that would forbid me from drinking outside of work? 

[Related but very different](https://workplace.stackexchange.com/questions/52042/can-my-employer-make-me-drink-alcohol)