[MerelyMortal]

That's a good source, however the issue that I see is that they already knew about it and kept him on.

You can't say it's okay to use marajuna and then later say, I had no idea he would test positive for marajuna. They should have reasonably known that he would test positive for marajuna.

Maybe it's not a medical discrimination case, but it's definately a case.

[kube-system]

It's a National Labor Relations Act case. Employees have the right to talk about unionization with their coworkers.

The employer constructed the other evidence as an excuse (which is what basically any employer knowledgable of the law does), but the previous approval would undermine the validity of that evidence.