Is dumpster diving against the law in the United States?

More info trash and privacy:

We need to examine the 4th Amendment which gives us protection against unreasonable search and seizures (without a warrant or probable cause). The 4th A. stems from English common law, as seen in a 1763 speech by William Pitt before the English House of Commerce, "The poorest man may in his cottage bid defiance to all forces of the Crown. It may be frail; its roof may shake; the wind may blow through it; the storm may enter; but the King of England cannot enter -- all his force dares not cross the threshold of the ruined tenement." [via Trash Archaeology]

California v. Greenwood (1988) examines what measures of privacy surround trash left out for garbage pickup. A Laguna Beach PD officer, Stracner, thought that Greenwood might be trafficking narcotics. Officer Stracner asked Greenwood's garbage collector to bring her Greenwood's trash. The collector complied, and after dumping out other refuse from the route, picked up the trash and delivered it to Stracner who found evidence of drug use in the bags.

After being jailed on felony narcotics charges and becoming released on bail, neighbors continued to complain about activity around the Greenwood residence. Another Long Beach officer, Rahaeuser, asked for trash from the garbage collector just as Stracner did, and a second warrant was issued for Greenwood, leading to arrest.

The decision in this case notes that, "we conclude that respondents exposed their garbage to the public sufficiently to defeat their claim to Fourth Amendment protection. It is common knowledge that plastic garbage bags left on or at the side of a public street are readily accessible to animals...children, scavengers...snoops...and other members of the public" citing People v. Krivda as an example.

Krivda says, "one must reasonably anticipate that under certain circumstances third persons may invade his privacy to some extent. It is certainly not unforeseen that trash collectors or even vagrants or children may rummage through one's trash barrels and remove some of its contents." Greenwood held that the, "Fourth Amendment does not prohibit the warrantless search and seizure of garbage left for collection outside the curtilage of a home."

See here for more related cases and related information on criminal procedure on the Emory School of Law website for cases by state where courts said that you do or do not have a reasonable expectation of privacy in garbage.

Note: I am not a lawyer.