Trivial? It might seem so, but it does actually fall well within the area the founders gave congress (surely this is both weights and measurements and interstate commerce).

"Fixing" the standard size would be fraud, as they don't sell the actual product that they claim to sell.

How about this: there's no legal requirement you label your products in any given unit, but if you choose 'inches', they have to be real 'inches'. You can use your own made-up unit, say 'oldnavies', instead -- just don't call them 'inches'.

(Even minarchists usually find laws -- common-law or legislative -- against commercial fraud acceptable.)

Hardly trivial when waist circumference is a predictor of heart disease.

http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt...

http://www.webmd.com/heart-disease/news/20050414/waist-size-...

Seems to me that "fixing" sizes would put pressure on people to lose weight, in the similar way that publishing calories on menus does.

State legislatures would also be an option.