Currently all meaningful investigative powers rest within the executive branch under DHS., However congress, and more specifically “The House” as the representatives of the people have the power to investigate through their executive oversight powers. It seems like the executive can simply “we don’t feel like cooperating even if you have the authority to investigate us” and Congress has no mechanism by which to force compliance. This policy would give each represented district (“the people”) the means to directly investigate their government in whatever topic they (through their representative) see fit to pursue.
I propose we give each member of congress two FBI agents and the discretion to open cases to investigate whatever they can show just cause to open an investigation into. This might be a separate agency created within the legislative branch create to aid in carrying out its oversight powers.
We could even limit it to not being usable against American Citizens, or outside the Executive Branch. But instead of Congress needing to ask the Executive to open an investigation into itself, Congress has direct authority and powers to get whatever information it needs to satisfy itself regarding what’s happening within the executive.
The government should fear its people, this investigatory power to expose corrupt activity and/or explain how/why certain things operate as they do ensure the government is acting in the people’s interests and not the government’s.