Via Mrt.com:

Due to demands by production company Lucasfilm, which owns the “Star Wars” franchise under its parent company Disney, the Midland-Odessa Symphony & Chorale will not feature the 501st Legion in its upcoming concert “Feel the Force. The 501st is a charitable organization of volunteers dressed in Star Wars character costumes. MOSC made the announcement Tuesday afternoon.
The 501st’s mission is to promote “interest in ‘Star Wars’ through the building and wearing of quality costumes, and to facilitate the use of these costumes for Star Wars-related events as well as contributions to the local community through costumed charity and volunteer work.”
Interestingly, on the Legion’s site, the organization describes its relationship with Lucasfilm as such: While recognized by the inclusion of the 501st name in official “Star Wars” material such as books and video games, the 501st is not affiliated with Lucasfilm nor do we rely on the company for bookings, event coordination, compensation or costuming materials. The 501st Legion is a volunteer fan organization.
But costumes are encouraged and the MOSC assures the May 7 concert will go on and tickets are available at MOSC.org.
From MOSC:
Executive Director, Jeannette Kolokoff remarks that “though the arrangement was made with the Lucasfilm-sanctioned 501st Legion over a year ago, Lucasfilm recently decided that they will not be allowed to perform at any concerts throughout the United States. We will not let this situation dampen our audience’s experience. Since we have promised our audience “photo opportunities” we encourage our audience members to wear costumes from any of our “space” movies featured in the concert. “In addition to “Star Wars,” MOSC will feature music selections from “ET,” “Avatar,” “Star Trek,” “2001: A Space Odyssey,” “Apollo 13,” and “Back to the Future.” Please keep in mind that weapons of any kind are not permitted in the Wagner Noël Performing Arts Center. MOSC will provide character cut-outs in the lobby for additional photo opportunities. We will let the force be with all of us as we enjoy some of the best space movie music ever created.