On May 28, 2013, the Federal Trade Commission (FTC) announced that it filed a complaint challenging Pinnacle Entertainment, Inc.'s proposed $2.8 billion acquisition of Ameristar Casinos, Inc. The FTC alleged that the acquisition, agreed upon on December 21, 2012, would violate Section 5 of the FTC Act and Section 7 of the Clayton Act by significantly reducing competition in the St. Louis, Missouri and Lake Charles, Louisiana casino markets. The complaint alleged that, in the St. Louis market, the acquisition would reduce the number of competitors from 4 to 3, give the combined entity a 58.4% share of the casino services market and increase the Herfindahl-Hirschman Index (HHI) by 1,667. In the Lake Charles market, where the parties are potential competitors, the FTC alleged that the acquisition would increase the HHI by 1,306. Post-HHI values in both geographic markets are alleged to be above 2,500.

The additional alleged anticompetitive effects include:

The FTC reasoned that as competitors, Pinnacle and Ameristar vigorously compete for customers, which results in:

The FTC alleged that because there are significant barriers to entry, including state laws preventing additional casino market entrants, the prospect of new entry would not be sufficient to mitigate the lost competition.