Prof. Amy Wax discusses the "disparate impact" theory: The Dead End of "Disparate Impact":
At the heart of the Ricci case was the doctrine of disparate-impact discrimination, which the Supreme Court first articulated in its 1971 decision in Griggs v. Duke Power Company. At issue in Griggs was the requirement that employees hired into service jobs at the power company's facilities had to possess a high-school diploma and achieve a minimum score on an IQ test. The plaintiffs argued that these rules disqualified too many black job applicants, thereby violating Title VII of the Civil Rights Act of 1964, which prohibits employment discrimination based on race, color, religion, sex, or national origin.
The Supreme Court agreed, ruling that job criteria with an adverse or exclusionary effect on minorities — even if those criteria were "neutral on their face, and even neutral in terms of intent" — could violate the Title VII ban on race discrimination in hiring. The Court further stipulated that employers could escape liability for "disparate impact" only if they demonstrated that their adverse selection practices had "a manifest relationship to the employment in question" or that they were justified by "business necessity." In examining the criteria for positions at the Duke Power Company, the Court found insufficient evidence to satisfy the job-relatedness defense, and so ruled against the utility.
Read the whole thing if you're interested. With all of the Federal legislation in recent years, employment law has become a hot area. A major expense for employers but one more gold mine for lawyers.