If a customs official thought you had contraband in 1789, he could search your person, open boxes on your ship, etc, without a warrant and without probable cause. See U.S. v. Ramsey: http://scholar.google.com/scholar_case?case=6107136132398268... (616-617).
The difference is that this "plenary power" to search at the border has different implications today now that people carry their whole lives around with them on their phones. But that seems to me to be a fault of the people rather than a fault of the law.
...a fault of the people rather than a fault of the law.
An entire philosophy of government, in a nutshell!
You know, it's actually OK to change laws that are bad for the people. For example, three of the four Alien & Sedition Acts were allowed to expire within three years (the fourth is only in force during declared wars), since no one actually liked them.
The difference is that this "plenary power" to search at the border has different implications today now that people carry their whole lives around with them on their phones. But that seems to me to be a fault of the people rather than a fault of the law.