And you're free to start a new wireless company. But try starting a new police force and you'll get arrested. Not the same.
https://www.aclu.org/blog/national-security/creating-your-ow...
https://en.wikipedia.org/wiki/Private_police#United_States
In fact, schools are a good example of this.
https://en.wikipedia.org/wiki/Campus_police#United_States
Creating a new police force is probably not any harder than making an MVNO and probably much easier than acquiring spectrum to create a real wireless carrier.
And you're free to start a new wireless company. But try starting a new police force and you'll get arrested. Not the same.