A Supreme Court ruling in 1998, California v. Greenwood, found that people have no expectation to privacy for trash they leave on the curb. Picking through publicly available trash is legal. However, many dumpsters are located on private property, explains FreeganInfo, which means dumpster divers may be prosecuted for trespassing. Some cities also have anti-scavenging laws which target dumpster divers, says HowStuffWorks.
Even though dumpster diving is not explicitly outlawed in most states, garbage pickers can be ticketed or arrested under related laws. FreeganInfo notes that police frequently ticket garbage pickers for littering and disorderly conduct. Anti-littering laws mean that dumpster divers should leave each dumpster location as clean as they found it, while disorderly conduct laws encourage dumpster divers to be polite. FreeganInfo advises garbage pickers to leave a site if asked, even if it is legal to search through the trash. Many businesses post anti-scavenger signs to reduce legal liability in case someone gets hurt from dumpster diving or sick from expired food, claim HowStuffWorks and FreeganInfo.
Trespassing laws are often used against garbage scavengers. However, "freegans" can be cited under trespassing laws even if the dumpster itself is on public property. Joseph Zanoli, a Boston Police Department spokesman quoted by Esquire, says that picking through rented dumpsters on public property is still trespassing because someone is paying a fee for the dumpster use.