15 U.S. Code § 2308 - Implied warranties
(a) Restrictions on disclaimers or modifications
No supplier may disclaim or modify (except as provided in subsection (b) of this section) any implied warranty to a consumer with respect to such consumer product if
(1) such supplier makes any written warranty to the consumer with respect to such consumer Product, or
(2) at the time of sale, or within 90 days thereafter, such supplier enters into a service contract with the consumer which applies to such consumer product.
(b) Limitation on duration
For purposes of this chapter (other than section 2304 (a)(2) of this title), implied warranties may be limited in duration to the duration of a written warranty of reasonable duration, if such limitation is conscionable and is set forth in clear and unmistakable language and prominently displayed on the face of the warranty.