An AG Jeans worker holds up a pair of AG jeans at the GQ & Nordstrom pop-up shop at Nordstrom's Treasure & Bond in New York.

You know those pricey, slim jeans that flatter ladies', um, backsides? They could ultimately cost even more if you buy them in Europe.

In May, the European Union imposed a tariff of almost 40 percent on American-made premium jeans, which account for 75 percent of the world's designer jeans market.