Ever seen one of those “warranty void if removed” stickers covering the screw holes on a gadget? Today, the FTC is reminding ASRock, Gigabyte, and Zotac that they’re illegal.

In fact, the FTC sent letters to ASRock, Gigabyte, and Zotac that suggest the FTC’s concerns aren’t just skin sticker-deep. Each letter tells the manufacturer to change its warranty and review its customer support practices to make sure they aren’t illegally threatening your warranty.

“Staff would be concerned if GIGABYTE, in practice, denied warranty coverage based on the warranty provisions quoted above or any similar provision,” reads part of one of the letters.

As of today, each of these companies’ warranties does include such a threat. The very first line in ASRock’s warranty reads, “Manufacturer’s warranty will be null and void if products are modified, damaged or otherwise tampered with, for example, the outer case is opened or additional optional parts/components are installed/removed.”

Gigabyte includes: “If the manufacturing sticker inside the product was removed or damaged, it would no longer be covered by the warranty.”

The particular right-to-repair law the FTC is invoking here isn’t one of the state-by-state ones that are now taking effect — it’s the federal Magnuson-Moss Warranty Act that attempts to keep companies from making bad warranties and misrepresenting them in the first place.

“The Warranty Act prohibits warrantors of consumer products costing more than five dollars from conditioning their written warranties on a consumer’s use of any article or service, such as repair service, which is identified by brand, trade, or corporate name, unless (1) the warranty states the article or service will be provided to the consumer for free, or (2) the warrantor has been granted a waiver by the Commission,” the FTC writes.

“FTC investigators have copied and preserved the online pages in question, and we plan to review your company’s written warranty and promotional materials after 30 days,” the agency is telling each firm.

iFixit has a blog on how “warranty void if removed” stickers may be legal in other parts of the world.