Russia, Ukraine, and the US are not signers of the voluntary ban.
Other than that I didn’t understand your post, it was contradictory.
“shouldn’t use them against countries that have rejected them.”
“Even if we have entered such a treaty, we should reserve the right to retaliate in kind.”
1. With respect to weapons banned by international treaty to which we are signatories, signatories retain the right to retaliate in kind.
I hope this is clear enough. But, international treaties are NOT agreements to unilateral disarmament. All countries retain the right of self defense.
2. With respect to weapons banned by international treaty to which we are NOT signatories, we’re good guys we shouldn’t use weapons against countries that have joined in those bans.
The argument is similar to treating all POWs humanely, to NOT initiating war, and to not using military weapons against our own population.