Julian Sanchez explains:
Most people assume their online communications enjoy the same Fourth Amendment protection as traditional dead-tree-based correspondence, but the statutory language allows the contents of “electronic communications” to be obtained using those D-orders if they’re older than 180 days or have already been “opened” by the recipient. Unlike traditional search warrants, which require investigators to establish “probable cause,” D-orders are issued on the mere basis of “specific facts” demonstrating that the information sought is “relevant” to a legitimate investigation. Fortunately, an appellate court has recently ruled that part of the law unconstitutionalmaking it clear that the Fourth Amendment does indeed apply to email… a mere 24 years after the original passage of the law.
He calls this "one more reminder that our digital privacy laws are long overdue for an upgrade."