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In what is seen as a big victory for civil rights advocates, the U.S. Supreme Court on Thursday rejected an attempt to narrow the scope of the Fair Housing Act, one of the nation's most important civil rights laws.

In the 5-4 vote, the "court acknowledges the Fair Housing Act’s continuing role in moving the nation toward a more integrated society," the court wrote. The ruling said a housing discrimination case can be based on disparate impact on minorities based on the federal fair housing law.

Passed in 1968 immediately after the murder of Martin Luther King Jr., the law explicitly allows lawsuits over decisions that intentionally discriminate in providing housing or the financing for it. But proving such illegal conduct is difficult, because anyone who wants to discriminate is usually careful to keep it from being obvious.

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Lower courts have endorsed the ability to sue for something else — the discriminatory effects of a housing decision. Lawsuits over zoning laws, lending practices, apartment occupancy limits, and leasing decisions depend on showing that racial discrimination was the result, even if it was not intended.

The case involved a Dallas, Texas civil rights group that sued a government agency responsible for allocating tax breaks to developers building housing for low-income residents. The group claimed that the agency channeled subsidies into minority communities, keeping developments away from white neighborhoods.

The group said those decisions frustrated the goal of reducing segregation and denied blacks the opportunity to move to safer neighborhoods with better schools.

The Dallas government agency said it was simply following a requirement to give preference to projects built in low income areas and did not intend to discriminate. Allowing lawsuits over the effects of its decisions, the agency said, would have the effect of forcing it to take race into account, thereby violating prohibitions against race-conscious decision making.

The NAACP Legal Defense Fund urged the court not to narrow the housing law.

"Neighborhoods that were purposely zoned or subsidized for only African Americans or only whites several decades ago remain similarly racially identified today."

As a result, the NAACP said in a friend-of-court brief, people who life in such segregated neighborhoods "face dimmer economic prospects, lower property values, truncated social and professional interactions, and inferior schools."