The Volunteer Suffers No Harm.

This is one for the lawyers and law students here. I am a little confused by a couple of things. I'd say for thirty years now I have believed in the no harm principle when it comes to laws. I first heard of the idea around 1988. I later found that the harm principle was conceived of at least in English law by 1859 with an essay by John Stuart Mill. There already was the very old concept in English and Roman law Volenti non fit injuria, the volunteer suffers no harm. Also I have heard people say for years that laws against vice crimes like prostitution would violate the separation of church and state because they are all ecclesiastical laws. The original crimes of ancient England didn't involve anything but property and the violation of people's rights like with murder or rape.

So what about prostitution laws? What about drug laws? Pornography and blue laws that say you can't drink on Sundays? Don't they violate all of those principles? Or at least the volunteer suffers no harm principle, which has always existed even in states with religious establishments like England?