In 1985 in Interpart Corp. v. Italia,[2] the Federal Circuit upheld the California anti-plug molding law against a preemption challenge, when it was invoked to stop copying of an automobile rear view mirror.
... [W]e see nothing in the federal patent statutes that conflicts with California's desire to prevent a particular type of competition which it considers unfair.Subsequently, in Bonito Boats, Inc. v. Thunder Craft Boats, Inc.,[3] in 1989 the United States Supreme Court held the Florida anti-plug molding law preempted because it partially duplicated and therefore interfered with federal patent law.
First, the Court brushed aside the Federal Circuit's characterization of the law as one preventing "unscrupulous" behavior: Appending the conclusionary label "unscrupulous" to such competitive behavior [i.e., copying] merely endorses a policy judgment which the patent laws do not leave the States free to make.
Sears and Compco extended that rule to potentially patentable ideas which are fully exposed to the public.
... By offering patent-like protection for ideas deemed unprotected under the present federal scheme, the Florida statute conflicts with the "strong federal policy favoring free competition in ideas which do not merit patent protection.