Back on topic, warrants for modern telecom, including internet messaging and VOIP are usually handled under Communications Assistance for Law Enforement Act (CALEA)
https://en.m.wikipedia.org/wiki/Communications_Assistance_for_Law_Enforcement_Act
Of course, NSA don’t need no stinking CALEA warrant
https://en.m.wikipedia.org/wiki/Communications_Assistance_for_Law_Enforcement_Act
Of course, NSA don’t need no stinking CALEA warrant