Difference between illegal and unlawful?

I’ve heard that these two terms are legally different, but have no idea how. Do they mean the same thing? If not, what’s the difference?

il·le·gal

adj.
Prohibited by law.
Prohibited by official rules: an illegal pass in football.
Unacceptable to or not performable by a computer: an illegal operation.
un·law·ful

adj.
Not lawful; illegal.
Contrary to accepted morality or convention; illicit.
Of, relating to, or being a child or children born to unmarried parents

well, one is used to define the other, so I’d say they are the same.
Legal denotes law, so il-legal is against the law.
Un-lawful kinda speaks for itself…

They could have a different legal meaning, in which case you’d best look it up in a “legal terms” dictionary.
Unfortunately, I have no such dictionary at my disposal.

hope this helps

I think that elfje has got it right. Here is what a leading legal-usage dictionary, written by the editor-in-chief of Black’s Law Dictionary, has to say:

Bryan A. Garner, A Dictionary of Modern Legal Usage 416 (2d ed. 1995).