Toei Animation announced that a man filed a lawsuit against their subsidiary, Toei Animation Incorporated. The plaintiff, Isaac A. Potter, Jr., served as his own lawyer when he filed in the United States District Court for the District of Colombia on December 9, 2010. Potter alleges that Toei's Knights of the Zodiac infringes on his copyrights and trademarks for Zodiac Knights 2000.

In 1995, Potter and his brother under the name Potter Boys' Creation, obtained a copyright for a drawing titled Zodiac Knights 2000. They filed a US trademark for Zodiac Knights 2000 ZK for numerous services, including clothing, games, and advertisements on February 24, 1997. The status of this trademark is considered "dead" as of April 9, 1998.

The brothers also filed a trademark for Zodiac Knights 2000 in Indiana on March 1, 2004. This trademark is considered "live." In May 2003, the two published a book titled Zodiac Knights 2000 Featuring Creatures of the Knights: Creatures of the Knights (A New Era) through 1st Book Publishing. The Potters filed a prior suit in Georgia's Fulton County against Cartoon Network on July 18, 2006. Cartoon Network filed two motions for dismissal in 2006, though both were denied. The court decided that the trademark for the title was not abandoned due to the Indiana filing.

Toei consulted their legal representation and assert that there is no legal grounds for the lawsuit. The company will fight the suit and try to dismiss it.