Does anyone seriously argue that President Lincoln needed warrants before allowing taps into Confederate telegraph communications?
However, Lincoln tapped telegraph lines 115 years before the passage of the 1978 Foreign Intelligence Surveillance Act, which requires the Executive Branch to notify the U.S. Foreign Intelligence Surveillance Court to seek a warrant within 72 hours after initiating electronic surveillance.

Telegraph lines in the Confederate States of America were in a discrete, specific geographic jurisdiction that had declared itself to be outside the jurisdiction of the United States.

Lincoln acted during a constitutionally declared war.

Telegraph lines were not private, individual communication. They were commercial and/or government information carriers. Only in rare and unique circumstances were private homes wired with a personal telegraph key. Messages were relayed by telegraph operators, via specialized offices, so there was a different level of privacy involved. So the constitutional issues of search and seizure were different.