The executive branch, particularly in the contemporary U.S., largely decides what policy outcome they would like first. Then they go digging for an existing sta

The executive branch, particularly in the contemporary U.S., largely decides what policy outcome they would like first. Then they go digging for an existing statute or 3 letter agency they can use to implement it. The legislative branch is at fault here for punting on their governing responsibilities. But it is true that via their oversight committees, they have constrained the actions of the executive, via new laws, based on classified intel. Foreign adversaries have no interest in domestic surveillance. There are many other things they'd like to get their hands on via discovery, though.