Sadly, as David Zarig observes, it seems possible:
Usually thought of as unusually receptive, for a financial regulator, at least, to legislative pressure, the SEC, perhaps in a testament to its recent obsession with insider trading, has done the opposite and filed suit against Congress, subpeonaing a congressman and his aide to see whether the aide disclosed news to a lobby/law firm about health funding that caused a bunch of stock prices to spike ahead of the announcement of the new policy. DOJ is in on the game as well.
Congress is, it appears, displeased:
“What the SEC has done is embark on a remarkable fishing expedition for congressional records -- core legislative records,” [congressional lawyer] Kircher said in a court filing. “The SEC invites the federal judiciary to enforce those administrative subpoenas as against the Legislative Branch of the federal government. This court should decline that invitation.”
The so-called speech and debate clause in the Constitution protects members of Congress and staff from any outside inquiry into legislative business.
It is pretty juicy, and we'll outsource why to corp counsel. I'm just ballparking here, but a conversion between an aide and a lobbyist would seem to be deeply, deeply covered by the speech and debate clause, as unappetizing as it might seem. Here's a note on the clause, and here's the Heritage Foundation, which does these recaps pretty well.
If the STOCK Act is going to have any teeth, Congress is going to need to figure out a system for waiving the speech and debate privilege in appropriate cases. The trouble, of course, is that most of Congress never really wanted the STOCK Act to have teeth.