Chris's analysis is on the ball as usual. Looking at it from an employee relations point of view, this is pretty crass, and I suspect it is a manager doing a bit of arse-protecting by threatening dire consequences, (because his boss has said something to him!) which, as Chris says, he would not be able to deliver. At the same time, I can understand the manager's concerns, under the current financial situation, if somebody was anti-social enough to wreck the facility. (There is always somebody......!)
However, one would hope that the employees concerned would want to ensure that the facilities remain undamaged for their own "convenience"! It may be best if they agree amongst themselves that they will do their best to ensure it, by a bit of peer pressure.
They then probably need to tell the manager that they really feel he is acting over the top with his comments and ask to speak to his/her boss to clarify the situation, and that they have discussed it amongst themselves, to be ensuring the nobody damages the facilities, in their own interests. I wouldn't get legalistic at this stage, and see what reaction they get from up the line. I think if the manager is acting over the top the last thing he/she will wnat is the overall boss getting involved, if he/she has stuck their neck out,
If both bosses think this is OK to do this, then wield the legal card.
However, an old boss of mine always used to say, that in these situations, it is important to make sure that the other side can walk away with their dignity intact for the sake of future relations, if those relations currently are not broke!!