I mean, you wouldn't think it'd need saying; but the memo clearly hasn't been passed on to Oxford United and Northern Ireland forward Gavin Whyte.
Footage, you see, has emerged of him and a mate giving big helicopters on a night out in Belfast last weekend.
Warning: Clip contains actual street wanking.
Strongly worded statement time!
First up is Oxford manager Karl Robinson: “It is totally out of character. Gavin is a quiet, respectful young man who is totally devastated by this: I have rarely heard anyone so remorseful for something that he regrets and knows he shouldn’t have done. Clearly he had drunk too much, and we will deal with that too, but whether you are a footballer or not that sort of behaviour is wrong on every level.
"We will sit down with Gavin today and we will remind him in no uncertain terms of his responsibilities. We have psychological and behavioural support here to help him get through this. He is a great kid and I hope the fans can forgive him for one moment of madness.”
Northern Ireland boss Michael O'Neill added: "Gavin’s actions in the video are clearly unacceptable and fall far below the standards that we expect from a Northern Ireland international. I know that Oxford United will discipline him appropriately for this significant mistake and both his club and the Irish FA will put in place measures to make sure that he learns from it."
And lastly, here's Gavin himself: "It was a moment of stupidity from me, one I regret very much and which I have to try and learn from. I can only apologise to anyone I offended and to those I let down by my behaviour. I am embarrassed beyond words but all I can do is try to move on, concentrate on my football, and make sure that nothing like this ever happens again."
Make sure. Nothing like this. Ever happens. Again.
I'm sure I speak for everyone when I wish him luck with his continuing battle with not wanking in the street. One day at a time, Gav. One day at a time.