Just reading the U.S. customs laws and found this...
In regard to copyright infringement, articles that are determined by CBP to be clearly piratical of a protected copyright, i.e., unauthorized articles that are substantially similar to a material protected by a copyright, are subject to seizure. A personal use exemption for articles, similar to that described above also applies to copyrighted articles for the personal, non-commercial use of the importer and are not for sale or distribution.
You may bring back genuine trademarked and copyrighted articles (subject to duties). Products subject to copyright protection most commonly imported include software on CD-ROMs, sound recordings, toys, stuffed animals, clothing with cartoon characters, videotapes, DVDs, music CDs and books. Products subject to trademark protection most commonly imported include handbags and accessories, and clothing.
weird that Hasbro hasn't just used this as a way of keeping their franchise under house rules.