I don’t think it’s “purposeful” as much as the fact that the fundamental fungibility of money makes it very hard to write legislation that covers a reasonable amount of loopholes. Or rather, while purposeful loopholes could exist, it’s very hard to prevent legislators trading stocks even if there were no deliberate loopholes.
Without getting into abstract legal philosophy, I think we can agree that this is effectively about insider trading (literally we're talking about trading on inside information) and insider trading is notoriously difficult to prosecute. Personally I think it's worth creating a law like our insider trading laws, with big punitive sentences to dissuade congresspeople from taking the risk. But I don't expect it to significantly outperform extant insider trading legislation.
