There are multiple definitions - click on the translation that matches your context.

不溯及既往的

形容词

full

non-retroactive

adjective

Definitions of non-retroactive

if a law, rule, or decision etc is non-retroactive then it does not have effect from a date before it was made

The EU has enacted a non-retroactive arms embargo (=a temporary stopping of trade, especially trade in a particular product).