35 U.S.C. 288 (pre‑AIA)  Action for infringement of a patent containing an invalid claim.

[Editor Note: Not applicable to to proceedings commenced on or after September 16, 2012. See 35 U.S.C. 288  for the law otherwise applicable.]

Whenever, without deceptive intention, 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.

(Amended Jan. 2, 1975, Public Law 93-596, sec. 1, 88 Stat. 1949.)