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Restriction requirements are often treated as administrative noise—something to get past on the way to allowance. The Federal 2025 decision in Focus Products Group International, LLC v. Kartri Sales Co. shows how dangerous that mindset can be. In that case, a species restriction and the patentee’s handling of it became the backbone of a prosecution history disclaimer argument that narrowed claim scope enough to wipe out two patent infringement wins. I. From hookless curtains