That's not true. Changing a stock sale plan in any way is considered insider trading. The window has nothing to do with whether it's legal or not. It's only used a risk mitigation and is up to company policy.

https://corpgov.law.harvard.edu/2013/02/05/rule-10b5-1-plans...

I think the point the cma was making is that this trick doesn't involve making changes to (formal) stock-sale plans. The formal plan is to sell regularly, and that remains unchanged, you just cancel it by hand habitually, except when you don't.

I am no lawyer, so I don't know if this is really allowed. My gut instinct is (a) no, it is not allowed and (b) there will always be some more subtle version of the tactic that is allowed.

Just hire a DDoS attack anonymously so your attempt to sell fails, pretend you've got nothing to do with it

It is a lot less clear cut than that: https://en.wikipedia.org/wiki/SEC_Rule_10b5-1#A_possible_loo...

Speculative execution bug causes speculative stock sale non-cancellation?

That's correct as I understand it, though there is a risk that some high-profile event will cause the media to whip up enough (understandable) public outrage to cause the SEC to actually, reluctantly fine someone for that.

Michael Milkin, the junk bond king of the 80s, realized that corporate bonds traded similarly to stocks, yet were not covered by insider trading laws.