Game doesn’t allow blocking creature if power over 2 by blocking creature but card decreases creature to power 2 and can’t block
1
vote

-
Rezzahan#77802 commented
That sounds like you were already in the blocker declaration turn based action. That is the only time you can declare blockers. Any creature you want to block with has to be able, or made able, to do so BEFORE that turn based action, so in the declare attackers step after attackers have been declared at the latest. You cannot block, make something able to block afterwards, then block with that something.