there isnt exactly a law against it, its simply they will shut you down if they get wind of it. the fact is, if one reads what they said at the time, they barely let one ounce 5% Lugols to be sold and said that if they detect any of those sales at a meth lab they will ban those too.
its all about the Iodine and not about the meth at all.
if you want pure Iodine you can buy KI by the truckloads and its 75% iodine. its easy to break the two elements apart.