> warrants seem to be required

Applies in the text you quoted, unlike true warrantless surveillance NSA-style?

You still have to get the warrant past a judge, and convince the judge of the higher bar for keeping the warrant secret.

I presume the distinction here could be between a search warrant, which you have to show the subject before entering their house, and a surveillance/wiretap warrant which you for obvious reason's don't.

(Meanwhile, FIVE EYES carries on as usual.)