35 U.S. Code § 298 - Advice of counsel
The failure of an infringer to obtain the advice of counsel with respect to any allegedly infringed patent, or the failure of the infringer to present such advice to the court or jury, may not be used to prove that the accused infringer willfully infringed the patent or that the infringer intended to induce infringement of the patent.
Except as otherwise provided in Pub. L. 112–29, section effective upon the expiration of the 1-year period beginning on Sept. 16, 2011, and applicable to any patent issued on or after that effective date, see section 35 of Pub. L. 112–29, set out as an Effective Date of 2011 Amendment note under section 1 of this title.