the feds have already used this in calif. on a mob guy. the info frrom green lantren was introduced as evidince, no warrents were used. unfortunatly the defendant changed his plea to guilty, so the constitutionality of it all is still untested.

zdnet had an article on it a few weels ago. they stated that a warrent was not always necessary, i forget exactly how it was stated, if the fbi had resonable suspicion, or some such ****.

MAGIC LANTERN installs so-called “keylogging” software on a suspect’s machine that is capable of capturing keystrokes typed on a computer. By tracking exactly what a suspect types, critical encryption key information can be gathered, and then transmitted back to the FBI, according to the source, who requested anonymity.
The virus can be sent to the suspect via e-mail — perhaps sent for the FBI by a trusted friend or relative. The FBI can also use common vulnerabilities to break into a suspect’s computer and insert Magic Lantern, the source said.

http://www.msnbc.com/news/660096.asp?cp1=1