Illegal? Why?

There are plenty of idiotic laws out there, probably (hopefully!) a relic of times gone by. But to this day, there are still prominent laws which crack down on things which do not hurt anyone (except perhaps the doer). Why should we, as a society, have laws concerning things which do no harm to others?

I guess I should start with what I think laws are for. Laws are how the government maintains the order of society. They prevents people from killing someone because they feel like it (or at least punishes them duly) and give a reason not to break contracts, or make life for someone else miserable.

As a general statement, people should be free to do what they like. But as Oliver Wendell Holmes Jr. (A supreme court member in the early 1900's) said, "The right to swing my fist ends where the other man's nose begins." Or, in other words, so long as your actions do not harm the property or body of another person, you can do it. I believe laws should uphold this - they should deter people from harming property which is not theirs, nor other people. That may be accomplished by putting a punishment on the act itself, or on intending to perform such an act. There may be other cases, but those are the only two which come to mind.

Examples of punishing an act are easy - murder, arson, theft, abuse are among acts punishable by law. Others, such as drunk driving, also go here. They are all acts which have a direct victim - the person, or person whose property has been hurt/destroyed/wounded/maimed (or in the case of murder, killed).

Examples of punishing intent are also easy to think of - intent to kill, intent to steal, etc. Generally these are most easily spotted on people with a record of performing the act in question, but are generally harder to spot. (And if police didn't have telepathy, damn, they'd be uncatchable!) Stalking may seem like it would fit under this category, but it's legally put under harassment, which makes sense, when you think about it.

Anyways, what about laws which don't fit under either of these categories? Like making gambling illegal? Or those which make polygamy, pot/other drugs (The distribution of such drugs to minors, however, should be illegal), prostitution, and adultery (I'm looking at you, Michigan and Wisconsin) all illegal? (Oh, and suicide has legal ramifications as well.)

I will note now that I do not necessarily advocate any of these things, but merely their decriminalization, as it makes no sense for them to be criminal activities.

Through this week, I'll be posting about these things, why they shouldn't be against the law, why other things (like flamethrowers, not getting your children immunizations, being a CEO of a company which screws up the economy) should be illegal or regulated.

Just to map out this week, here's the list of topics I'll go through:
Consent, implied consent, and gambling
Relations, sexual or otherwise (polygamy & adultery)
Drug laws (and why their inconsistency/lack of effectiveness makes them moot)
Control over one's body (suicide)
Busybodies and how religion factors in
Some things which should be illegal, or regulated.

Hopefully, this will get me back in the regular habit of posting again.