This is the kind of thing that would be relatively easy to convince nations to sign up to*; actually enforcing, I suspect you're right.

* there's not an obvious benefit to being the one nation that says "you know what? We want to be known as 'the nation whose biolab insecurity wrecked the world', because taking blame works out so well for everyone.", though I'm fairly sure a large portion of the world will be totally willing to wargame the impact of hosting a lab as a deadman switch so nobody else attacks them first…