Under the 1975 Magnuson-Moss Warranty Act, which the commission cited in its letter, companies can't put repair restrictions on their products unless they provide the parts or services for free or receive a waiver from the FTC. Thomas B. Pahl, Acting Director of the FTC's Bureau of Consumer Protection, said in a statement:

"Provisions that tie warranty coverage to the use of particular products or services harm both consumers who pay more for them as well as the small businesses who offer competing products and services."

Since warranty stickers are a common sight on popular consumer electronics, like say, the PS4 and various phones, it was pretty unclear whether the law covers products much cheaper than cars. As Motherboard noted, though, the letters made it crystal that it also covers electronic devices, so long as they cost more than $15.

The FTC asked the six companies to review their warranty notices and make sure that they don't "state or imply that warranty coverage is conditioned on the use of specific parts of services." It will then review the companies' websites after 30 days, warning the letters' recipients that "failure to correct any potential violations may result in law enforcement action."