"May contain" should provide legal protection. It may be compliance tits in some cases, but that's better than forcing the addition of a compliance ingredient.
reply> "May contain" doesn't provide legal protection
replyYes, this causes problems.
> and then if you make it a standard there needs to be testing for compliance
Why would there need to be any additional testing? If anything I'd expect "may" foods to need less testing than an accident-prone "no" food.