The Civil Rights Act of 1964 didn't forbid any particular racial or sexual configuration in school or the workplace. An employer or admissions officer is free to choose, so long as he doesn't choose for the wrong reason. But, according to law, they could not be consciously created. You can hire only white males, but you cannot intend to hire only white males. This is where the trouble begins.
Every decision is made from a mixture of motivations.
Not even the actor himself can fully know what went into a decision. Certainly the government cannot. But by forbidding certain kinds of discrimination, the government gives itself power to define what constitutes evidence for malintent. Courts, it's hardly surprising, took the easiest path. To prove discrimination, look for circumstantial evidence.