Can the police station check the content of mobile phone short messages?

Go to Mobile or Unicom Telecom, and you can definitely find it! ! ! ! ! ! ! ! ! ! ! ! ! ! Of course, to the public security department.

Q:

Mobile, China Unicom and telecom insiders also need the password of the mobile phone card to find it, right? Public security departments should also have good reasons to check by mobile, China Unicom and telecom, but they can't check easily, can they?