I think the insider trading laws don't require motive - just that they had private information or used their position of influence and that they benefited from a related trade. The rules for executives at companies usually requires them to file any trade plans related to their company stock prior to actually making the trade, which would at least prevent the short term plays like the Pelosi example. Even tech people at trading companies are subject to restrictions in what they can trade, even if they aren't looking at the financial data.
Stupid insider trading, where someone gets a tip and then trades on it, is well enforced. It's easy to catch ex post facto and the people doing it are generally of the mind that everyone is insider trading and so they're unlikely to get caught.
The problem is in the grey areas. Take the Pelosi example. The material nonpublic information was her personal policy position. Assuming she acted purely venally, are your own intentions insider information? If I know I'm going to get Chipotle for lunch tomorrow, is it insider trading to buy Chipotle shares?
If, on the other hand, her husband took a conversation he had with her about policy and then traded on it, that would be insider trading. Unless they did it over text message, however, the odds of proving it are zilch.
Once she announces it in the media, wouldn't it be a professional policy opinion? CEOs are similar. They can believe what they want, but what they say to the media can be punished (like Elon was). The real sticking point is how is she of one opinion then flip to the complete opposite the next day without giving a reason. If they have to report their intended trades then it could avoid this short term play.
Spouses and household members are held to the same restrictions as the regulated individual, regardless of the conversation or not. The only reason it's hard to prove is because they are in a position of power. The SEC would jump on any normal people doing the same thing.
Regarding the Pelosi example, it's even worse than what was suggested above. The TSLA trade was placed a few days before Biden came out and said they planned to buy EVs for government vehicles, which was an announcement that directly caused TSLA to spike up the second it was broadcast to the market.
Again though there's plausible deniability, as you say. It needs to just be outright banned.
