If a State requires a certain label, that's usually fine as long as it doesn't conflict with federal labeling requirements or regs. But you've got to accomplish

If a State requires a certain label, that's usually fine as long as it doesn't conflict with federal labeling requirements or regs. But you've got to accomplish essentially the same thing you would need to on the federal level, except in one or more states. As for "voluntary" labeling, the rules have evolved to be weird sometimes, but usually if the EPA claims a chemical is safe, a company can't "override" that on their label. Besides industry specific regs, libel and anti-competitive laws come into play as well. So even if the EPA let's you add a warning to the label, doesn't mean a competitor won't sue you for doing it. Another concern is tacit admission of guilt. It strengthens the claims made by users/plaintiffs from before a warning was put on the label. There's a lot of conflicting cya aspects to consider. For a non EPA example of this, look at the battle over milk labeling re: rBST.