I don't think so. In fact, here's an excerpt from Part 9-10 of the Six Flags-SEC agreement:
"We have the exclusive right on a long-term basis to theme park usage of the Warner Bros. and DC Comics animated characters throughout the United States (except for the Las Vegas metropolitan area), Canada, Mexico and certain other countries. In particular, our license agreements entitle us to use, subject to customary approval rights of Warner Bros. and, in limited circumstances, approval rights of certain third parties, all animated, cartoon and comic book characters that Warner Bros. and DC Comics have the right to license, including Batman, Superman, Bugs Bunny, Daffy Duck, Tweety Bird and Yosemite Sam, and include the right to sell merchandise using the characters. In addition, certain Hanna-Barbera characters including Yogi Bear, Scooby-Doo and The Flintstones are available for our use at certain of our theme parks. In addition to annual license fees, we are required to pay a royalty fee on merchandise manufactured by or for us and sold that uses the licensed characters. Warner Bros. and Hanna-Barbera have the right to terminate their license agreements under certain circumstances, including if any persons involved in the movie or television industries obtain control of us or, in the case of Warner Bros., upon a default under the Subordinated Indemnity Agreement."