I came across this with the Eleanor lawsuits - https://www.caranddriver.com/news/a42233053/shelby-estate-wi... - and while I believe that that instance Eleanor falls on the "this shouldn't have been copyrightable" (took a bit to get there), the question is "what protects the representation of Darth Vader?"
In general it tends to be ignored and tacitly encouraged... but it isn't protected.