35 U.S.C. § 288 - U.S. Code - Unannotated Title 35. Patents § 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.