35 U.S.C. § 288

Action for infringement of a patent containing an invalid claim

Whenever a claim of a patent is invalid, an action may be maintained for the infringement of a claim of the patent which may be valid. The patentee shall recover no costs unless a disclaimer of the invalid claim has been entered at the Patent and Trademark Office before the commencement of the suit.

( July 19, 1952, ch. 950 , 66 Stat. 813 ; Pub. L. 93–596, § 1 , Jan. 2, 1975 , 88 Stat. 1949 ; Pub. L. 112–29, § 20(h) , Sept. 16, 2011 , 125 Stat. 334 .)