The Fourth and Sixth Amendments prohibit government officials from in any way intruding on the privacy of lawyer/client confidential rights of citizens.
The very fact that this material is seen or read by a government official constitutes a core violation. It would be the same if the government surreptitiously recorded a confession of a penitent to a priest, or a description of symptoms by a patient to a doctor, or a discussion of their sex life between a husband and wife.
The recourses for intrusions on the Fourth and Sixth Amendments are multifold: the victim of the intrusion can sue for damages; he or she can exclude it from use by the government in criminal or civil cases; or the victim can demand the material back. But none of these remedies undo the harm to privacy and confidentiality done to the citizen by the government’s intrusion into his private and confidential affairs.
Many TV pundits are telling viewers not to worry about the government’s intrusion into possible lawyer/client privileged communications between President Trump and his lawyer, since prosecutors will not get to see or use any privileged material. This is because prosecutors and FBI agents create firewalls and taint teams to preclude privileged information from being used against the client in a criminal case. But that analysis completely misses the point and ignores the distinction between the Fifth Amendment on the one hand, and the Fourth and Sixth Amendments on the other.
The Fifth Amendment is an exclusionary rule. By its terms, it prevents material obtained in violation of the privilege of self-incrimination from being used to incriminate a defendant – that is to convict him of a crime. But the Fourth and Sixth Amendments provide far broader protections: they prohibit government officials from in any way intruding on the privacy of lawyer/client confidential rights of citizens. In other words, if the government improperly seizes private or privileged material, the violation has already occurred, even if the government never uses the material from the person from whom it was seized.