The Federal Trade Commission has sent warning letters to six major companies over illegal language and practices involving the warranties for things like automobiles, cell phones, and video game consoles.

Thanks to some light sleuthing from Ars Technica, it appears that both Nintendo and Sony are likely among the recipients of those letters.

Earlier this week, the FTC released a public reminder about a 1957 law that governs what companies can and can’t include in their manufacturer warranties The posting lists three examples of what it calls questionable provisions.

However, as Ars points out, the example text of “This warranty shall not apply if this product ... is used with products not sold or licensed by [company name]” lines up with the language used in Nintendo’s warranty and “This warranty does not apply if this product ... has had the warranty seal on the [product] altered, defaced, or removed” matches wording found in Sony’s warranty.

A third example, seemingly taken from auto manufacturer Hyundai’s warranty, attempts to bar people from using non-manufacturer parts in repairs, lest they void the warranty.

In all three cases, manufacturers aren’t legally allowed to make such restrictions in the United States.

Specifically, the Magnuson-Moss Warranty Act states that statements like those are generally prohibited unless companies provide parts and services for free or have received a waiver from the FTC.

“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,” said Thomas B. Pahl, acting director of the FTC’s Bureau of Consumer Protection, in a statement.

The six companies that were sent warning letters have 30 days to revise any promotional or warranty information to remove language that implicitly states or implies “warranty coverage is conditioned on the use of specific parts of services.” Following that, the FTC plans to check back in with each company and will potentially seek out legal action if violations still exist.