The Daily Cow

According to this flag etiquette site,

The flag should never be used for any advertising purpose. It should not be embroidered, printed or otherwise impressed on such articles as cushions, handkerchiefs, napkins, boxes, or anything intended to be discarded after temporary use. Advertising signs should not be attached to the staff or [hall yard].

Hm. I guess if you were to find a law that is quite violated, its this one. And this is a law set by the US government too.