The Republicans attempted to make such a distinction in the FISA bill currently before the House. The Republicans planned to offer a motion that politically vulnerable Democrats would have a hard time voting against. The amendment would have said that nothing in the bill could limit surveillance of Osama bin Laden and terrorist organizations.
This would have established that Osama and terrorists get less protection than ordinary citizens. The democratic leadership didn't like this idea and the FISA bill has been pulled for rethink.
A reasonable compromise would allow FBI/CIA/NSA surveillance ( tap phones, read email, open US mail, demand billing records, hack into computers) of foreign (Russian) spies, members of terrorist outfits on the Attorney General's list, and foreign nationals on foreign soil without any sort of warrant. Surveillance of US citizens at home or abroad , and foreigners on US soil need a warrant from a court.