In the letters the FTC sent out, it asked the six companies to revise their warranty notices and make sure they don't "state or imply that warranty cover is conditioned on the use of specific parts of services". The FTC cites the Magnuson-Moss Warranty Act, which in 1975 determined that manufacturers can not restrict repairs on devices which come with warranties, and the FTC Act.
Having your smartphone serviced by an unauthorized third party will most certainly void its warranty.
The FTC gave examples of "questionable provisions", one of which matches the wording used by Hyundai, requiring customers to use company parts, while another used by Sony for its Playstation 4 gaming console voided warranties if a warranty seal was "altered, defaced, or removed". Or you actually read the manual or visit a product website where it states any warranty is void if you don't carry out repairs using official parts and service providers. The commission requests that each of the six companies review their warranty materials and correct their policies within 30 days.
Some of the misleading statements cited by the FTC included: "The use of [company name] parts is required to keep your. manufacturer's warranties and any extended warranties intact" or "This warranty shall not apply if this product.is used with products not sold or licensed by [company name]".
Companies who sell products globally and then refuse to deliver warranty on these products in Countries such as Australia and the US are already facing problems the same goes to organisations that have stickers that void warranty.
However, the actual legal enforcement of those warranty stickers has always been debated, and in a new letter, the FTC is taking the time to remind some companies that it doesn't view the stickers as enforceable.
Companies that have any question about their illegal practices regarding warrantys can go have a peek at FTC dot ORG where the FTC's Consumer Response Center released a statement.