The single most effective weapon of American white supremacy has been social convention. As long as the majority of Americans were convinced that it was importatn to keep blacks and whites separate, then oppression followed. Most significantly, the law followed. As law, the justification for oppression and suppression of African Americans took place under the color of moral and civic authority. Of course there were other moral forces at work in this country as well. Soon enough of these forces gathered strenght and mounted opposition ot the civic authority.
At this point in our nation's history, much of the civic authority for racial oppression has been destroyed. There are few, if any, remaining laws which give separate rights according to race. However, the law is always subject to social convention. If the majority if Americans could be convinced of the importance to keep blacks and whites separate, then new laws would be crafted.
Despite the existence of law, there are conventions within groups of americans about racial mixing.
Today, the legacy of American white supremacy exists primarily in the form of residential segregation. I attribute most racial inequality to the fact and presence of ghettoes - those areas, created specifically for the purposes of keeping racial minorities apart and away from the mainstream of American society.