Generally, tie-in sales provisions arenít allowed. Thatís a provision that requires a consumer to buy an item or service from a particular company to keep their warranty coverage. Here is an example of prohibited tie-in sales provisions.
To keep your new Plenum Brand Vacuum Cleaner warranty in effect, you must use genuine Plenum Brand Filter Bags. Failure to have scheduled maintenance performed, at your expense, by the Great American Maintenance Company, Inc., voids this warranty.
However, a warrantor can require a consumer to use select items or service if theyíre provided free of charge under the warranty.
US Code - Title 15, Chapter 50, Sections 2301-2312
"(c) Prohibition on conditions for written or implied warranty; waiver by Commission No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the Commission if -
(1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and
(2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefor."