A good idea, and not a new idea.
"
No first use (NFU) refers to a pledge or a policy by a nuclear power not to use nuclear weapons as a means of warfare unless first attacked by an adversary using nuclear weapons.
Countries pledging no-first-use:
China
India
Russia
United Kingdom
THE UNITED STATES in 1994 https://en.wikipedia.org/wiki/Nuclear_Posture_Review
Pakistan
Israel"
https://en.wikipedia.org/wiki/No_first_use