"States rights" is widely viewed as a racist dog-whistle [1]. States rights doesn't have to be racist, although it is very often linked that way [2].

The war on drugs was instituted as a racist policy [3]. It's quite likely that the main motivation here is using drug laws to punish people of color.

[1] http://www.slate.com/articles/news_and_politics/history_less...

[2] https://www.theatlantic.com/magazine/archive/2001/03/getting...

[3] http://www.cnn.com/2016/03/23/politics/john-ehrlichman-richa...