It is sad about what happened to the 4th amendment.
Citizens have a right to privacy by default. It is only when the citizen allows it or when a court authorizes it through a warrant to be able to break a persons privacy.
It doesn't matter where the information is store and who owns the storage the device. The person has a expectation from the constitution that the information will not be unlawfully used.
If they have to get a warrant to search a persons safety deposit box in a bank then they have to get one to search a persons cloud account. It is really that simple.
If they have to get a warrant to tap or listen in to telecommunication lines then they have get one if they want to read emails as well.