Back in my college days, the local club adopted a no-baggy pants dress code, among other fashions, like sideways caps, jerseys, bandannas, etc. There was an immediate outcry that this was racial discrimination, since black guys were more likely to wear those fashions than white guys.
Wayside Dress Code
This article claims that discrimination was going on between equally soggy pants depending on who was wearing 'em, but iirc, the outcry on campus was that the dress code itself was inherently racist.
I could see how that could be used as a sneaky way to discriminate against a particular group of people. Even if people from other groups also wear that style, if the style is predominately worn by a particular group of people, the rule would disproportionately effect them.
This was back in 2005, though, so by now, perhaps, the style is just as likely to be worn by any group.