A virtuous ex-cop writes in his blog, Cop in the Hood:
When you board a plane, both you and your carry-on bags are searched. A civilian employee of the Transportation Security Administration may open and search your checked luggage as well. Although primarily looking for security threats, workers report any illegal or suspicious objects to a supervisor or law enforcement agent, even if the object represents no danger to the flight.
Two legal concepts allow both you and your bags to be searched despite the Constitution’s protection against unreasonable search and seizure. By being in an airport and trying to board a plane, the Supreme Court says, you have given “implied consent” to being searched. The “plain view” principle, according to the court, states that whatever law enforcement legally finds, feels or sees — even if unrelated to the original investigation or search — is fair game for arrest and prosecution.
Using security and terrorism as justification, the government is beginning to extend airport-like implied consent zones to more and more of the public sphere, including the entire Boston subway system. Before the Democratic convention, daily commuters, anybody approaching a national political convention, and drivers on vital bridges and tunnels were told to expect random searches without a warrant. Fourth Amendment protection against unreasonable search and seizure does not apply.
When police are granted greater rights to search without probable cause, they will use these rights. Therefore it’s essential to consider the implications of implied consent and plain view searches in the public sphere.