A U.S. congressman is calling for Comcast Corp. “to be broken up,” days before the cable giant is set to face off against Byron Allen, an African American Hollywood entertainment mogul, in a Supreme Court case that some say could make it harder to bring racial discrimination lawsuits.

In a letter Thursday, Rep. Bobby Rush (D., Ill.) told Comcast CEO Brian Roberts that he is “dismayed" that the company might undercut the country’s oldest civil rights law, the Civil Rights Act of 1866. Rush is a member of the House Energy and Commerce Committee.

A Comcast spokesperson said Friday that Rush has no power to break up Comcast.

Rush claimed that Comcast had failed to live up to its promises at the time of acquiring NBCUniversal of making its programming more inclusive. Those promises, critical in getting influential minority groups in Washington to support the merger, were merely for “political expediency,” Rush contended.

“Comcast has enjoyed the largesse — as has the cable industry, in general — of the African American and other minority communities, and has reached such prominence that it now disregard these communities with a cold, callous corporate insensitivity that is stultifying, arrogant, harmful, and intensely painful," Rush wrote.

At the heart of the dispute is a 2015 lawsuit in which Allen sued Comcast for $20 billion, alleging that the cable company discriminated against him based on race when it refused to carry his channels.

Comcast has maintained that business reasons, not race, are behind its refusal to carry Allen’s channels, most of which focus on courts, comedy, and pets. After he filed suit, Allen’s Entertainment Studios also bought the Weather Channel, which Comcast does carry.

The Supreme Court is set to hear the case on Wednesday.

Allen cited Section 1981 of the 1866 law, first enacted to provide basic contract rights to newly emancipated black Americans after slavery ended, as a basis for his suit. That section says that all people in the United States have the same right to engage in contracts.

"We are not seeking to roll back any civil rights laws — all we are asking is that Section 1981 in our case be interpreted the same way it has been interpreted for decades across the country,” a Comcast spokesperson said Friday.

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Allen’s suit was rejected three times by a district court judge who did not find that racism was a plausible reason for Comcast’s decision, Comcast officials said. However the Ninth Circuit Court of Appeals said Allen needed to show only that racial discrimination could be one factor in the refusal to do business.

Comcast responded by appealing to the Supreme Court seeking a ruling clarifying that race must be the only reason — not just a motivating factor — behind any allegedly discriminatory decision.

In August, the Justice Department filed a brief siding with Comcast. Other business organizations, such as the U.S. Chamber of Commerce, have said in briefs that the Ninth Circuit ruling would encourage frivolous discrimination claims. In late September, more than a dozen civil rights organizations supported the Ninth Circuit’s interpretation while not taking a position on the merits of Allen’s lawsuit.

Mary Frances Berry, a lawyer and professor of history at the University of Pennsylvania and a former chair of the U.S. Commission on Civil Rights, said she supports Allen’s case against Comcast.

“They want to narrowly define the act to kill his complaint before he gets to have it investigated through the discovery process," Berry said. “They want to stop him.”

Rush ended the letter by saying, “Simply put, it is my belief that the Comcast Corp. needs to be broken up.”