Ferguson was one of 20 state attorneys general who accused Phusion Products of advertising to the underage.
The agreement prohibits the company from promoting binge drinking and from advertising on college campuses.
Phusion has also agreed to stop producing drinks that combine alcohol and caffeine.
Four Loko originally contained both alcohol and caffeine, but the company removed caffeine from the formula after Washington state banned the drink in 2010. That ban came after nine Central Washington University students became ill after drinking Four Loko at a party.