Since the disclosures of Edward Snowden in 2013, the U.S. government has assured its citizens that the National Security Agency (NSA) cannot spy on their electronic communications without the approval of a special surveillance judge. Domestic communications, the government says, are protected by statute and the Fourth Amendment.1 In practice, however, this is no longer strictly true. These protections are real, but they no longer cover as much ground as they did in the past.When Congress wrote the Foreign Intelligence Surveillance Act (FISA) in 1978,2 it was trying to set a short leash on the NSA at home and a long one overseas.3 The NSA could not tap into communications inside the United States without following strict rules, but it had a free hand to intercept data elsewhere. Even now this sounds like common sense. The NSA is not supposed to spy at home, but spying abroad is central to its job. One policy problem we face today, however, is that the realities of the modern Internet have blurred the distinction between spying at home and spying abroad.