In 1966, the Rev. Martin Luther King Jr. led a march through the streets of Chicago to protest the housing segregation that plagued that city and many others throughout the nation. Less than two years later, King was assassinated, but not before he shone a light on the devastating harms of segregation and the crisis of unfair housing. Just a week after King's assassination, Congress honored his legacy and changed the course of history by passing the Fair Housing Act with broad bipartisan support. This law worked to dismantle the decades of public and private discrimination which, in the words of George Romney, then-secretary of Housing and Urban Development, created a "high income white noose" around the black inner city. Yet today, this landmark civil rights law is in jeopardy, as the U.S. Supreme Court prepares to hear a case about whether to overturn foundational fair housing protections.

The Fair Housing Act has helped the country make great strides by combating policies that discriminate against families, the poor, African-Americans, Latinos, other communities of color and people with disabilities. The law has been instrumental in eliminating policies like racially exclusive zoning rules, subsidies for segregated communities and redlining, all of which perpetuated racial segregation, stripped individual African-Americans of their right to choose where to live and relegated entire communities to ghettos of inferior opportunity.

Although the Fair Housing Act has already been successful, it still has more work to do because the legacy of these discriminatory policies persists in many areas. Ferguson, Mo., offers a contemporary example of such ruinous effects. While the recent crisis in Ferguson arose from racial bias in policing, the underlying dynamics can be traced to discriminatory housing polices. In 1876, the city and county of St. Louis were formally separated, spawning various communities outside the city, like Ferguson. White residents eventually fled to these newly developed communities, which used racially restrictive covenants, among other tactics, to exclude African-Americans.

These discriminatory covenants remained in place until 1948, when an NAACP Legal Defense and Educational Fund lawsuit prompted the Supreme Court to declare them unconstitutional. In response, many St. Louis suburbs implemented exclusionary zoning restrictions, creating white affluent enclaves and relegating African-American families to urban areas and inner-ring suburbs like Ferguson. Federal and local officials further supported these arrangements through discriminatory subsidies, loan requirements and public housing programs.

The vestiges of these policies continue to drive residential patterns in Ferguson and numerous other cities. Thus, government-sponsored segregation, along with private acts of discrimination, are directly responsible for today's racial isolation. The Fair Housing Act remains essential to redress entrenched segregation in places like these and to remedy the situation for future generations.

Yet in the same week that we celebrate King's life, the Supreme Court threatens to upend a key provision of the act, and with it a crucial tool for eradicating residential segregation. Shortly, the court will hear arguments in Texas Department of Housing and Community Affairs vs. Inclusive Communities Project. At stake is a legal protection that ensures that banks, landlords and others use policies that apply fairly to everyone. The protection also prevents mortgage lenders, for example, from adopting policies that seem neutral in theory but that unfairly exclude or segregate particular communities in practice. Over 40 years of legal precedent uphold this central protection of the Fair Housing Act, including rulings by 11 federal circuit courts across the country, and enforcement efforts by Democratic and Republican presidents alike dating to the Nixon administration.

The outcome in this case will determine whether the Fair Housing Act can continue to be used, as it has for decades, as a tool to replace discriminatory policies with ones that roll back the tide of residential segregation. This is a unique time when the nation's eyes have been refocused on the racial dynamics that undergird our society. Let us seize the moment and celebrate King's vision and endeavors — and hope that the Supreme Court will do the same by allowing his work to continue.

Sherrilyn Ifill is president and director-counsel of the NAACP Legal Defense and Educational Fund.