Yeah, EO 12333. Section 1.12b(13) what you refer to? A loose interpretation could allow that, especially given the relevant 'as directed by' clauses'.
Look, simply: dig it, you want to capture and connect signals from Bad Guy A to Bad Guy B. Fine; it may or may not be as crazy as some of the stuff show up in movies and on TV, but what with proxies and VPNs and all, the comms can route through all kinds places, in and out of US.
So to connect the dots you gots to follow the stuff. OK, I get it. I was at least reading about this stuff thirty years ago, not long after I dug into the seminal stuff on packet-switched networks.
Had the admin come to the people, especially after 9/11 and the weirdly-named Patriot Act, and said, hey, to help try to track some of these guys we gotta Hoover everything and hang on to it for a few weeks, and if it happens to pass through or involve stuff inside US we'll do it with specific and highly-limited warrant and all, and then everything not needed gets thrown away.... and oh, by the way, no, we have no interest, let alone the time, energy, money, or even capability of reading Aunt Milly's email, is that OK with you?
Instead all this comes out of the secret places where we're repeatedly assured that everything's above-board...
Now, you wanna talk intel gathering? Or how our gov doesn't trust us? Or their historical excuses for so much of what's been classified for seventy years or so, national security, when in fact the great bulk of 'secret shit' is that way to prevent the people from knowing it (when all the bad guys already do) or, commonly enough, to prevent embarrassment to highers? (Last I looked, two presidential studies and one either via Congress or a contracted third-party all came to the above conclusions, btw; the first study was done at the behest of Ike.)
Color me really simple - I tend to get rankled by under-handed crap. Protecting then minutiae of operational ways and means is one thing; hiding the whole shebang behind the magic curtain because we're too simple and have 'no need to know' is another entire.