"Laws" dictating which restroom anyone is allowed to use, or must be allowed to use, are both unnecessary and harmful.
If you own a restroom, feel free to make up whatever rules concerning their use you want. If I don't like your rules, I won't use your restroom and may not do business with you.
If you fund your restroom through theft ("taxation"), you don't own it and you don't get to make up rules concerning it. Thieves don't own the property they possess.
If you are uncomfortable in a restroom with another person- any other person at all- get out of there. To worry about whether they "should" be in there is ridiculous.
If attacked by anyone, anywhere, fight back with everything you've got. Again, whether the person "should" be in that restroom is a distraction- they are attacking and need to be stopped.
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