@email@example.com I’m 99% sure, that won’t be the case. I’d be really surprised, if the instances, willing to host illegal content, weren’t somehow blocked by default.
Even the sites hosting gore and archiving illegal shooting cams, always have an effective way to remove illegal pornography. If anyone made a site without that option, no-one would ever want to host it and the only users happy to stay on it, would be pedophiles.
There are a few Mastodon instances like that, made by and for pedophiles, hosted in places with loose laws, but they’re completely defederated, even from those ran by “free speech absolutists”, as well as the few, straigh up advocating neo-nazism.