Lawfare: Online Service Providers and the Fight Against Child Exploitation: The Fourth Amendment Agency Dilemma by Jeff Kosseff:
Public-facing platforms such as social media services can give law enforcement a direct view into illegal online activities, providing crucial evidence for criminal investigations and prosecutions. But not all online communications are open to the public. Before law enforcement can search the contents of emails, chat logs and other private communications, the Fourth Amendment generally requires that they obtain a warrant supported by probable cause.
What about the private companies that provide the services? Can’t they automatically or manually search their users’ private accounts for evidence of a crime and then share that information with the government? The answer to that question, from a Fourth Amendment perspective, is not always easy, and it points to one of the most substantial barriers to public-private partnerships in investigating distributors of child sex abuse material and other illegal content.