https://www.techradar.com/news/those-warranty-void-if-removed-stickers-are-illegal-says-us-consumer-watchdog

Warranties can be somewhat fickle things. Whether you have a games console, a mobile phone or even a car, you’ve probably noticed in the small print that the manufacturer will refuse to honor the warranty on that product if you use what it deems to be unauthorized repair services or unauthorized third-party accessories – or, heaven forbid, if you break the seal of that 'Warranty Void if Removed' sticker.

According to US consumer protection watchdog the Federal Trade Commission (FTC), however, such policies are illegal. On April 10, the FTC announced that it had sent letters to six companies warning them that their conditional warranty practices violate the 1975 Magnuson-Moss Warranty Act, which states that no manufacturer is allowed to put restrictions on the repair of a device it offers a warranty on.