Cool, raw, legit, looking good. It is often used in a greeting, or describing how someone or something looks, acts, appears, or works. Also, legal often preceeds the adjictive "pretty".
"Lookin' pretty legal" Describing how someonr looks good.
"That shirt's pretty legal" Describing how a shirt looks good.
"That bike is pretty legal" Describing how a bike looks good.
Because unfortunately; that's just how the world works. I punish you and live. OR I punish you and die. My life is in your hand. Even if I have no legal recourse.