There are two exceptions, but they are very narrow.
It's common for manufacturers of cars, video game consoles, and other products to insist that consumers will void their warranty if they use unauthorized fix services or unauthorized third-party parts.
Unless warrantors provide the parts or services for free or receive a waiver from the FTC, such statements generally are prohibited by the Magnuson-Moss Warranty Act, a law that governs consumer product warranties. The Playstation 4 has various stickers that must be broken to open the device that explicitly state that tampering with them invalidates the warranty. iPhones and MacBooks don't have a warranty-voiding sticker, but Apple Geniuses are trained to look for clues that would tip the company off to the fact that the device has been opened. Motherboard spotted an FTC press release in which the Commission announces it has sent letters to six companies, warning that their stickers are in violation of a longstanding law.
The FTC warning states that language like "this warranty shall not apply if this product.is used with products not sold" and requiring warranty stickers to maintain a warranty are all illegal. I have a feeling that this one in particular is aimed at smartphone companies.
The news comes amid reports that users of the Apple iPhone 8s may find themselves unable to use the touchscreen after downloading the recent iOS 11.3 update, if they had the screen repaired by a third party other than Apple.
The final issue that the FTC has raised pertains to warranty void stickers.
Sony's warranty states that "this warranty does not apply if this product. has had the warranty seal on the PS4™ system altered, defaced, and removed".
This could be a major win for consumers: more repairs and service locations would be allowed under warranty, and modders of game consoles may be able to indulge their hobby without trying to hide it from the manufacturer. Otherwise, legal actions will be taken.
Affected companies have 30 days to review their websites to see whether warranty conditions have been removed or changed.
KitGuru Says: Warranty stickers are a nuisance but they are so common at this point that it would be hard to stop them from circulating. Now the FTC says these kinds of policies are illegal.