When Bobby Kennedy snooped on MLK

Even before the Patriot Act, there were exceptions under federal law to our guarantee of privacy under the 4th amendment.

"One was for so-called "pen-trap" orders. To obtain from a telephone company the numbers dialed to and from a particular telephone, officers must get a pen-trap order from a judge. They do not need to show probable cause, but must certify that the information is needed for an ongoing criminal investigation. The reason for the lesser standard is that these records are far less intrusive than wiretaps and physical searches.

Another major exception was for matters before the Federal Intelligence Surveillance Court. Congress created the court in 1978 following scandals revealing that U.S. intelligence agencies had spied on hundreds of thousands of American citizens, most notably the Reverend Martin Luther King Jr." [Bobby Kennedy was the AG for this snooping]

(from "The Patriot Act" - Constitutional Rights Foundation)