That's something I never understood (and admittedly never researched either). Isn't there something in the constitution about freedom of association?
Edit: My mistake, it was 1958, but they took legal action in the 1960s (Loving vs Virginia, 1967), and despite the Supreme Court's ruling, some states kept such laws on the books as late as 2000 (Alabama), which is actually probably what you were referring to.
The comment by the judge in 1958 is (almost) unbelievable:
Almighty God created the races white, black, yellow,
malay and red, and he placed them on separate
continents. The fact that he separated the races shows
that he did not intend for the races to mix.
Presumably God wasn't as fussy about non-red races in the legal profession in North America.I wish the federal government and every state had a lawspeaker -- for statute laws anyways.