See AMD says no to thermal grease.
One problem here in the UK is that system integrators like the ability to put together machines that they think are the best, and also like a choice, like their customers do, too.
The US act in question is called the Magnuson-Moss Warranty Act. As a reader points out, this legislation specifically stops "tie in" sales, where a vendor might say that the overall warranty is voided unless you use a specific item.
There is an exception, and that involves the vendor demonstrating to the satisfaction of the Federal Trade Commission (FTC) - yeah, that lot - that other manufacturers' products won't work properly with the CPU.
So AMD will have to go along cap in hand to the FTC and show, for example, that Arctic Silver thermal goo, which does work with its CPUs, isn't a suitable er, solution.
There's more on this interesting piece of legislation, here. µ