X, Y, and Z fast-food burger chains have a secret meeting in Captain Tony's Bar in Key West where they all agree to divide up the Keys into three geographic territories - upper, middle, lower including Key West - each to receive an exclusive territory, and where they also promise not to compete with each other in their respective territories. This agreement is:
Legal if they can demonstrate that it is good for the consumer since the companies will now be able to compete more effectively against other fast-food businesses, especially Subway, which now has surpassed McDonald's in the number of worldwide outlets, and KFC.
Legal as long as the territorial division is a fair one and there was no fraud or mistake present in the transaction.
Illegal pursuant to the Per Se doctrine of anti-trust law.
Legal pursuant to the Rule of Reason doctrine of anti-trust law.