My bad - it’s the 22nd Amendment.
And if you read my other takes on this (for example, this one from 2011), no, the 12th Amendment does not say that he cannot be Vice President - well, at least not because he would have already served two terms as President. If you think otherwise, then show me where - but if you say “the 22nd Amendment makes him ineligible,” read the fifth word of that Amendment carefully.