That seems like something that should be handled with a simple takedown request and those behind archive.is would almost certainly comply. 99.999% of people using archive.is are using it to bypass news article paywalls nothing more. Which, if we're honest, is the real reason why the FBI is going after them.
Personal anecdote but I almost never use these archive sites to bypass paywalls. I only use it when I want to see how establishment news sites somehow sometimes accidentally tell the truth, then, when they get the call, they try to purge their original reporting. Again, it might be my personal bias, but in my opinion, this is the main reason they are going after them. Because these websites let people prove the hypocrisy and the lies.
I remember that when[0] Reuters took down that one story about organized crime, and further DMCA'd the Internet Archive to take down their version, archive.ORG cheerfully did the memory-hole thing—while archive.IS stayed up.
If the (Western) internet were to turn into a monoculture of Western-domiciled big corporations, that kind of censorship would be *effective*. Our systems aren't robust against bad-faith actors attacking the free flow of information. (And the root cause of the planet-spanning censorship cascade in that example was, unambigiously, bad actors. A crime syndicate based in India).
The fact the internet is global and freely connects to legal jurisdictions and cultures very different from the West's, is to the West's benefit: it creates an escape-hatch for things that fall between the cracks of our nascent totalitarian technologies.
1. Put up CSAM on your unlisted domain briefly.
2. Archive page and delete site.
3. Send people archive link.