Smarter bad actors could still do it without being detected. Hiding an encrypted message in unsuspicious messages isn't that difficult. I really don't see the point of having such a law.
> also allow some higher-but-not-peak intensity software to be written with GC where it might not be today (games come to mind), although that could actually encourage more energy usage than what it would save.
Just look at Minecraft for that (it's written in Java). A recent version created up to 200 MB of garbage per second!