The program does not represent a violation of the Constitution because the Fourth Amendment does not protect dialed phone numbers, in contrast to the content of the communications, because individuals lose privacy over those numbers when they are given to the phone company. The Constitution protects the content of the communications, whether it be a phone call, e-mail, or old-fashioned letter. And Congress approved a change to the FISA statute to allow such collection, and a court of federal judges approved it. And as commander-in-chief, the president has the wartime authority to find and intercept enemy communications, known as signals intelligence. Analyzing such metadata — what is sometimes called data mining — is perhaps the most effective way to find terrorist cells in the U.S. and stop future attacks because the Obama administration has dropped our best methods for producing intelligence (the detention and interrogation of al-Qaeda leaders).

The revelation of broad e-mail surveillance is more troubling, but it is because we don’t know the program’s scope. If the program only intercepts the content of e-mails for foreigners abroad, as is being reported, there is no constitutional violation. As the Supreme Court has made clear, the Fourth Amendment does not protect the communications of non-U.S. persons that take place abroad. In fact, the Justices reached that conclusion because they observed that it would be impossible for the U.S. to fight a war against a foreign enemy if limited by the Fourth Amendment. …