If the law enforcement is trying to find a murderer, or they're trying to catch a drug lord or trying to prevent a school shooting, and they have leads and they have suspects, then it's perfectly fine for them to tap the suspect's phone, and to intercept his Internet communications.
법 집행 기관이 살인범을 잡으려 하거나 마약 사범을 잡으려 하거나 학교에서 총기 사고를 막으려고 할 때 단서가 있고 용의자가 있다면 용의자의 전화를 도청하거나 인터넷 통신을 감시하는 건 당연하죠.