The question before the judges during oral arguments on Wednesday morning was this: Does that language require that the discrimination be intentional, or does it allow plaintiffs to claim a discriminatory effect, regardless of intent?

If ever there was a legal issue that appeared to be settled, this is it. Over four decades, every one of the 11 federal appeals courts to consider the law has found that it covers claims of discriminatory effect. A 2013 regulation issued by the Department of Housing and Urban Development provides explicitly for such claims.

This legal consensus is easy to understand. The law was meant to be a broad and powerful tool against the effects of unjust discrimination in housing. Today, persistent housing segregation remains a fact of life for many blacks, with a range of adverse consequences including poorer economic prospects, lower property values and inferior public schools.

The ability to show discriminatory effect has only become more important as intentional discrimination has become harder to prove. To take one prominent example, the Justice Department relied on it to negotiate the largest-ever fair-lending settlement — $335 million — with Bank of America in 2011. The bank’s mortgage unit, Countrywide Financial, had charged higher average fees and interest rates to black and Latino borrowers than to whites with the same credit risk, a practice that former assistant attorney general Thomas Perez called “discrimination with a smile.”

Even so, the Roberts court had agreed on two earlier occasions to review the scope of the act, suggesting to many people that it is not happy with the law’s mainstream interpretation. The cases were withdrawn or settled at the last minute, with help from the federal government and civil-rights groups worried about how the court would rule.