29 U.S. Code § 623 – Prohibition of age discrimination | U …

An applicable defined benefit plan shall be treated as failing to meet the requirements of paragraph (1) unless the terms of the plan provide that any interest credit (or an equivalent amount) for any plan year shall be at a rate which is not greater than a market rate of return. A plan shall not be treated as failing to meet the requirements of this subclause merely because the plan provides …

: https://www.law.cornell.edu/uscode/text/29/623