This seems like the textbook definition of market division.

From the first Google result for "antitrust law market division" (https://www.classlawgroup.com/antitrust/unlawful-practices/m...)

> In almost all circumstances a market allocation agreement will be illegal under antitrust law. Federal antitrust law treats a market allocation amongst competitors as a per se violation of the antitrust laws. Other types of potentially anticompetitive behavior are only illegal if their anti-competitive effects outweigh their pro-competitive efficiencies. But per se violations are automatic violations of federal antitrust law.