The American Cable Association has asked antitrust law enforcers at the Department of Justice to open an investigation into the business practices of Comcast-NBCU, “focusing on harms stemming from the dominant communications firm’s control of cable systems, TV stations, and regional sports networks concentrated in some of the largest local markets in the country.” The agency’s request came in a Nov. 6 letter to Makan Delrahim, Department of Justice’s Assistant Attorney General for Antitrust. In the letter, ACA and its members “pledged to cooperate fully to assist in the investigation, including by providing information about Comcast-NBCU’s practices.” “By opening a formal investigation, the DOJ, which has already put Comcast-NBCU on notice, can take the next step to gather facts about the company’s activities and ensure consumers and competition are protected. Given the enormity of Comcast-NBCU’s market presence and incentive to engage in anticompetitive harm, such an investigation is fully warranted,” ACA President and CEO Matthew Polka said in statement. President Trump highlighted the ACA’s request this afternoon in a tweet. Shares of Comcast are down 30c to $38.04 in afternoon trading.