Very different kind of trust. To serve a warrant at my home, agents of the government have to be physically present, and they have to give me a copy of the warrant printed on a sheet of paper. The physics of that situation provides auditability. If the warrant was not genuine, the people who served it would go to prison.

Cryptographic back doors are totally different. It is not possible to build a back door that has auditability built into its basic physics the way warrants do. That the thing that William Barr doesn't understand. His mindset is something like, "If we can send a man to the moon, surely we can make a way for law enforcement to break encryption that doesn't threaten people's rights." Well, no, we can't. Sending a man to the moon is merely difficult. A back door that only "the good guys" can use is actually impossible.