You caught where he said, '... though states rights have been weakened over time..."

https://en.wikipedia.org/wiki/National_Minimum_Drinking_Age_...

"The National Minimum Drinking Age Act of 1984 (23 U.S.C. § 158) was passed on July 17, 1984 by the United States Congress. It punished every state that allowed persons below 21 years to purchase and publicly possess alcoholic beverages by reducing its annual federal highway apportionment by ten percent."