Earlier quoted context omitted.
> "voluntary trade" makes it sound like said trade wasn't actually illegal Just because something is illegal doesn't mean it's wrong.
That is completely true. But the police don't arrest people for breaking ethical principles, they arrest people for breaking laws. So also, in context, not entirely relevant.
> But the police don't arrest people for breaking ethical principles, they arrest people for breaking laws.
...Unless the police officer has ethical principles, in which case they will refuse to obey unfair laws. I remember watching an interview with a Danish cop that refused to arrest someone for smoking marijuana inside their own house. I think it's fair to say the government police system encourages unethical people to become cops.