Proposition 65 is a California state law and cannot be enforced with companies that do businesses outside of the state of California. Furthermore, California can only enforce the law were companies ship and/or sell their products in California.
In addition, companies required to display Proposition 65 warnings on their products sold in California are not required to do the same when they sell in other states. While companies that do not do business in California are not required to add the warning notices on their products, many do anyway to avoid possible litigation (in the instance that their product ends up being shipped or sold to California).
If a product that is intended for sale outside of California makes it into the state of California without a warning label, it becomes subject to Proposition 65 litigation.