Critical Gender Theory
Critical theory of any kind stems from Marx. "Critical theory focuses on political, cultural, economic, and social relationships within a culture, particularly as they are related to what groups have power and which do not". This tells that the groups who hold the power are always going to be the ones making the decisions, thereby creating rules that the others follow.
Gender is something that goes beyond simply biology. Gender is something that is socialized within the way society views boys and girls. Gender is social, cultural, behavioral, and psychological. Gender is something that falls into more of a spectrum, rather than a binary scale like biology. A person's biological sex is physical and specific traits, that is much simpler than gender.
Those who don't want to allow transgender people to be able to go into the bathroom they feel most comfortable using feel that way because they think it is wrong. They think this idea is "wrong" because that is what the people in power have always said. This is a way of those who are in power controlling social structures through telling people what they should think about this idea versus letting them think freely about this idea. Because those in the courts are the ones with all the decision power over whether or not they are going to pass this bill, once they have put it into law or made their decision, that decision then sets precedent. This standing decision then is telling the other citizens that they should agree with whatever they ruled "right".