As far as I'm aware, the anti-BDS laws only pertain to performance under governmental contracts or similar, or are merely statements of position without legal effect.
Is there a law that prohibits individuals who are not operating under such a contract from boycotting?
All anti-BDS that I am aware of operate through government employment and contracting.
I would however clarify your statement in that the scope often extends not just to the work under contract, but personal and professional behavior outside the scope of contract.
Yes, but it's still under the authority of the contract. That means that expressing support of a boycott is not illegal, it's just grounds for termination of that employment.
