Star Wars helmets are industrial props, not works of art.
(So, why is this interesting? Well it’s very interesting to a British prop designer and George Lucas. On Wednesday Andrew Ainsworth, said prop designer, won a court battle against US film company boss George Lucas over his right to sell replica Stormtrooper helmets. Declaring the helmets functional and not artistic, means they are not subject to full copyright law, and their only copyright protection is 15 years from the date they were marketed. So, if you want to dress up, you are free to do so.)