IIRC insider trading is not illegal for Congressmen and Senators.
No, it isn’t. But it should be.
The STOCK Act is actually one of the few things Obama got right: https://www.cbsnews.com/news/obama-signs-stock-act-to-ban-congressional-insider-trading/ A loophole exists though (of course): It’s an open question whether an intent to vote one way or another is “material non-public information.”
I know Wikipedia isn’t the greatest source but this is a pretty generic explanation.
STOCK ACT …. The Stop Trading on Congressional Knowledge (STOCK) Act of 2012 (Pub. L.Tooltip Public Law (United States) 112–105 (text) (PDF), S. 2038, 126 Stat. 291, enacted April 4, 2012) is an Act of Congress designed to combat insider trading.
Laws only work when they’re enforced.
https://en.m.wikipedia.org/wiki/STOCK_Act