Actually, just monitoring (electronically) a cellphone conversation is against the law--that's why all of the scanners produced since the late 80's have the cellphone frequencies blocked. The 1986 ECPA made it illegal to listen to cellphone conversations. Prior to that, the 1934 law that governed radio communications made it illegal to repeat what you heard from monitoring any radio transmission that wasn't intended for public use. Now, if some jerk, say Chuckie Schumer, talks too loud and can be overheard by anyone near him, well, that's certainly not illegal to listen to and report.
Drudge's report indicated that it was overheard. He does not say who Chuckie was talking to, or what the other person was saying.
Then how did that sweet old couple intercept Newt's cell phone conversation and tape it?