I think you missed what I was getting at, you are going to have manufacturers and reviewers all over the world ...
Good luck to you in solving the world’s audio reviewing problems.
... just talking about the first amendment is irrelevant ..
It may be irrelevant to you, but the First Amendment is anything but irrelevant. As I noted, it protects those publishing in the US, notwithstanding your claim to the contrary:
First amendment is applicable only if both manufacturer and the reviewer are in US.
Those enjoying First Amendment protection would be foolish to compromise any of it by entering into any sort of agreement that would seem to appeal to you.