how and why some conduct is considered unlawful?

[lawlearner6]

[JackDanielsU]

because conducting yourself in a "bad" way is. well bad...behave yourself and youre not breaking any laws

[tamborine]

We are the law makers; decided by majority votes. We are bound by rules & laws for the good of all.

[factorfiction]

Because it contravenes the law.
Can you be more specific - it's not really enough to simply quote the question you have been set for homework as we don't know the context of the question, the level at which you are studying, etc.

[sara3]

this is a rather basic question from someone calling themselves "lawlearner".

surely the first question of the course, lol!

[lawlearner6]

there is no need to be bitchy is there

[buildersmate]

It tends to depend on the quality of the original question.

[boxtops]

it's considered unlawful because the laws of the land say you can't behave in that way.

[Gmcd01]

To start (and I do mean just to scratch the surface), read:

James Fitzjames Stephen- "Liberty, Equality, Fraternity"
Find the Hart/Devlin debate
Find some articles in the Cambridge Law Review
JS Mills' "On Liberty"

This isn't some one word answer from online, this is a question that tests the very basis of our society! Think about Nazis (Godwin's Law), how does the law making there shape our thoughts? This will take hours of your time, and rightfully so. I prefer the views of Lord Patrick Devlin, but you can make up your own mind.