I work in a "workshop" type atmosphere. There are 4 women and 30 to 40 men working in the area. There is a Men's room and what is supposed to be a Ladies room. However, the plant manager insists upon using the Ladies room, but only for a specific body function. In the past he has walked in on me twice, because he just unlocks the door and walks in without knocking first. Due to my complaint a bar latch was installed on the inside. Never the less I feel he should NOT be using the Ladies room at all. There have been many times that one of us girls has needed the facility, but he is in it. Shouldn't he NOT BE USING this rest room at all? I find it offensive and distasteful and I can't seem to find a specific law (L&I or otherwise) in PA that states whether a man can or can not use the Ladies room. Both the plant manager (the offender) and the General Manager of the company find my annoyance quite funny. I need to be pointed in the right direction in my search. Hope you can help me? Thank you.
Sue Goodwin

I don't think they would laugh at a sexual harassment discrimination suit.

Now in NY there was a recent case for the subway where the court ruled that men who were cross dressers can use the ladies rest room.

But if there is a lock on the door that should end the issue.

I couldn't find anything specific from a quick search. So I would go to:
Occupational Safety and Health Administration - OSHA HOME PAGE or The U.S. Department of Labor Home Page, Secretary of Labor Elaine L. Chao
And see if there is a contact point where you can e-mail for an answer to this.

From the sounds of what you describe, this is a private bathroom with only 1 toilet. So when you are inside it, you lock the door and no one else can use it.

Therefore, I don't see why they need to have a man or woman's washroom.

Is the man's washroom a private washroom as well?

If it is, why not just use that one?

Take a look at Scott's link, but I do not think there is anything that can be done about it. But I hope there is. Good luck.

If he does so discretely and under locked door and his use of it doesn't in any way impose on your privacy when you go to use it, then I don't think you've got much to stand on.