I am surprised no one in the media is raising the point, that regardless of the legal status of any corrections or clarifications, the KLB can be easily turned into law. All the American legislators would have to do is to attach the corrections to any bill coming to the floor for voting. That way the addendum could be turned into law.
It is a common practice among legislators to get their pet-projects approved this way. The method is also adopted for low-profile weapons transfers meant for the allies; eg weapons to Israel. If Senator Kerry is serious about his statement then he could add the addendum to another bill.