Changes to the law are only considered ex post facto laws in the United States when they bring about a criminal punishment - So prosecutors couldn’t charge Trump if the 22nd amendment was changed to only allow 1 term, for example. So if the 22nd amendment was altered to allow for more terms, it would not be considered an Ex post facto law
Also within this very hypothetical scenario, the act of seeking a third term is after the hypothetical amendment, so there is no ex post facto in any case.
https://en.wikipedia.org/wiki/Ex_post_facto_law
Changes to the law are only considered ex post facto laws in the United States when they bring about a criminal punishment - So prosecutors couldn’t charge Trump if the 22nd amendment was changed to only allow 1 term, for example. So if the 22nd amendment was altered to allow for more terms, it would not be considered an Ex post facto law
https://en.wikipedia.org/wiki/Calder_v._Bull
IANAL, but this is what I was taught in high school
Also within this very hypothetical scenario, the act of seeking a third term is after the hypothetical amendment, so there is no ex post facto in any case.