> civil servants can't and should not be expected to stop enforcing the law

In general, criminal law permits but does not mandate prosecution and every prosecution is a judgement about not only the law but policy priorities. This argument is almost completely vacuous where it concerns offenses primarily against the state (it has some weight in equal protection terms when there are victims besides the state and the issue is whether the state is discriminating among victims on improper grounds in the manner in which it chooses to prosecute or not prosecute offenses against them.)