Theoretically, laws are enacted to prevent people from doing activities that would harm others, right? For example, it's illegal to kill people or do them bodily harm.
However, many thousands of people are in prison right now for crimes which actually do no harm to anyone outside of themselves. There are two immediate examples which come to mind, but remember these are not the only examples - merely the obvious ones.
First I guess would be prostitution. Now I know that terrible things happen when pimps and etc. get involved, but if in a given situation there are two people who wish to exchange money in order for the occurrence of sexual activity, what is the problem? If there are only two (2) people involved in the situation, and both of them agree that the situation is A-OK, why should the government be involved at all in the transaction? I would even go so far to say that, were the activity NOT illegal, the involvement of pimps, etc. would not be necessary.
Another obvious and easy example is smoking mary-jew-anna. If I have a pot plant growing in my yard (which I may or may not actually have
) and I take to smoking its bounty on a regular basis, why should I have to be afraid of the government? If I were to get robbed at gunpoint, and call the cops, it is more likely that I would get hammered for the pot plant than the robber would get pursued and prosecuted. Does that seem right to you?
Other examples of consensual laws would be polygamy (assuming all parties are consenting and of age), underage drinking, adultery, porn, abortion, using drugs in general, pre-agreed-upon euthanasia, suicide, or any other crime in which all the participants are consenting...