...TECHNICALLY it would be stealing (the trash either belongs to whoever put it there, or else to the trash collector)...
But LEGALLY, trash/garbage is considered abandoned and that the owner gave up legal ownership by throwing it away.
That’s why cops can conduct searches of refuse like that for evidence without a warrant. You have no expectation of privacy in your garbage once it’s outside for pickup.
The precedent for this was set by a Dylan fan who continually went through his garbage outside searching for memorabilia. The Court said no problem.
Certain states, however, don’t have a free-for-all attitude toward garbage. In Texas, for example, the courts have found that depositing trash in a garbage bin does not constitute abandonment, per se, but rather the transfer of property from the owner to a waste-hauling firm.
http://www.slate.com/articles/news_and_politics/explainer/2009/05/hands_off_my_garbage.html
A. J. Weberman was the perp.