Federal officeholders vote on legislation, set regulatory priorities, and make decisions that directly affect which industries succeed and which ones don't. They also, in many cases, actively trade stocks in those same industries. That is a conflict of interest so obvious it barely needs explaining.
The rule is simple: while serving in federal public office, you cannot trade stocks. You can keep every position you hold. Your 401(k) stays yours, any options or holdings you have when you take office remain yours, you just cannot buy or sell while you are one of the people pulling the levers that can make businesses rise and fall.
This is not punitive. It is the same standard we hold financial advisors to, and they have far less power over the market than a sitting senator. You are welcome to return to trading the day you leave office. And if you "just can't" then you need to find a different job.
Enforcement requires an independent accountability body with actual teeth: mandatory disclosure, real audits, and consequences that mean something. The honor system has not worked.