] In order to stop and search any suspect, not just a
] terrorism suspect, law enforcement need only wait for a
] person to enter an implied consent area such as a subway
] or a shopping mall. Their action justified by the "war on
] terror," police may then conduct a full search. The true
] object of the search -- most likely drug possession, but
] any contraband will do -- is unrelated to terrorism.
]
] Of course people shouldn't break the law or carry illegal
] objects. But the difference between civilian employees
] searching for bombs in airports and government agents
] conducting random searches for suspicious objects is the
] difference between preserving a free society and creating
] a police state.
]
] In airport security today, items deemed suspicious are
] not necessarily dangerous: Large amounts of cash, pirated
] CDs, pornography and, of course, drugs -- not just
] illegal drugs but even prescription drugs in certain
] circumstances. In fact, controversial books can be
] grounds for further investigation and arrest. Such a
] standard, even if established in airports, is
] unacceptable and must not be allowed to spread to our
] streets and subways.

This is an older article Bruce Schneier posted in the comments of Barlow's last post.

Balancing Security and Liberty (washingtonpost.com)