I'm not sure what you're saying. Here are all the situations I can think of in, like, a minute:
1) An actual transgender person who was born male and has transitioned to female wants to use the men's room. This law stops them. So now we someone who is essentially biologically female being forced to use a male restroom. Though this person will still be using the women's room because you can't fucking tell. They go to the bathroom and leave to go about their day, and no one is bothered.
2) A transsexual person who is male but considers himself female wants to use the women's restroom. He is dressed as a woman because that's how he associates, but has had no surgeries. This law stops them. Though this person may be able to use the women's room based on how well they pass as a woman. They go to the bathroom and leave to continue their day, and no one is bothered.
3) A criminal dresses as a women to use the women's room to assault/peep/commit crime. He shouldn't ever be allowed to, but again... he may be able to if he passes well. He goes into the bathroom and COMMITS A CRIME. This is already illegal and he should be prosecuted! This law about who can use what restroom should stop him, but it doesn't come into play because he roll a 20 stealth anyway and just walked in to commit his crime. We should stop these people, but this law doesn't do a damn thing about them; they are already going to do it, regardless.
4) A guy puts on a wig to use the women's restroom. He doesn't consider himself trans in any way. He also doesn't commit a crime (for whatever reason... it's your example, I guess). He just pees in a women's toilet and leaves to go about his day. This law should stop him! But if it didn't... who was hurt? All the guy did was pee. He didn't peep or assault anyone or take photos or anything. He just has a weird toilet preference, I suppose.