Heck, Linus Torvalds should just add an amendment to the next release of the Linux Kernel that makes it illegal to use in any jurisdiction that requires age verification laws.
This would obviously cause such a massive disruption (especially in California) that the age laws would have to be rolled back immediately.
This seems like a no-brainer to me but I am admittedly ignorant on this situation. I'm sure there's a good reason why this isn't happening if anyone cares to explain.
If it's not (fully) your code, you aren't free to set the licence conditions; Linus can't do that without getting approval from 100% (not 99% or so) of authors who contributed code.
What one can do is add an informative disclaimer saying "To the best of our knowledge, installing or running this thing in California is prohibited - we permit to do whatever you want with it, but how you'll comply with that law is your business".
A "Linux distro" is not the Linux kernel. It's possible for some distros to add such license terms to their distribution media, but others like Debian and Debian-based ones adhere to the GPL so no go.