> "no Warrants shall issue, but upon probable cause"
As a non-legal expert, the way this feels to me is that asking for a backdoor is like preemptively issuing a warrant for everyone on the grounds that they might commit a crime in the future that you'd want to investigate. Thus backdooring iOS is tantamount to issuing an unlimited warrant for everyone, which is exactly what the Fourth Amendment is trying to prevent.
As a non-legal expert, the way this feels to me is that asking for a backdoor is like preemptively issuing a warrant for everyone on the grounds that they might commit a crime in the future that you'd want to investigate. Thus backdooring iOS is tantamount to issuing an unlimited warrant for everyone, which is exactly what the Fourth Amendment is trying to prevent.