Did you read the entire ruling?
This remains a fundamental rule of federal antitrust law and draws a line between legal independent decision-making on the one hand and illegal joint or monopolistic activity on the other.
Q: I own a small clothing store and the maker of a popular line of clothing recently dropped me as an outlet. I'm sure it's because my competitors complained that I sell below the suggested retail price. The explanation was the manufacturer's policy: its products should not be sold below the suggested retail price, and dealers that do not comply are subject to termination. Is it legal for the manufacturer to cut me off?
A: Yes. The law generally allows a manufacturer to have a policy that its dealers should sell a product above a certain minimum price, and to terminate a dealer that does not honor that policy. Manufacturers may choose to adopt this kind of policy because it encourages dealers to provide full customer service and prevents other dealers, who may not provide full service, from taking away customers and "free riding" on the services provided by other dealers. However, it may be illegal for the manufacturer to drop you if it has an agreement with your competitors to cut you off to help maintain a price they agreed to.
Your claim was that YiHi couldn't set minimum prices and enforce them. This is not true, as generally it has an individual right to set prices however it pleases and terminate supply to anyone who doesn't abide by such prices. Separate from that is when parties collude to set prices, such as if one or more dealers convince a manufacturer to adjust minimum authorized prices or restrict deliveries to hurt another dealer.