The Federal Trade Commission sued PepsiCo on Friday, alleging that it has engaged in illegal price discrimination by giving unfair price advantages to one big-box retailer at the expense of other vendors and consumers.

The Robinson-Patman Act was passed in 1936, but the federal government stopped enforcing it during the deregulation of the 1980s. The FTC resumed its enforcement in December when it sued Southern Glazer’s, the largest U.S. distributor of wine and spirits.

The U.S. Federal Trade Commission sued PepsiCo on Friday for offering preferential pricing to a large retailer, whom a source familiar with the matter confirmed was Walmart .