Pushing aside the creative shortcomings of Disney’s Oz: The Great and Powerful — and boy, there are many — there is one scene director Sam Raimi gets absolutely right.

The prologue of his prequel to Victor Fleming’s beloved The Wizard of Oz (1939) introduces us to a conniving, womanizing, big-thinking circus illusionist (James Franco) who is chased by angry carnies and escapes in a hot air balloon. The balloon is swept up in a tornado and lands in the CGI-splotched land of Oz.

Shot in 4:3 ratio, in smoky black and white, the scene is a handsomely rendered old-school prelude to two hours of candy-coloured landscapes and 3D-enhanced screensavers. The original film similarly opened in sepia-toned monochrome (though it, of course, was not lathered in digital artifice).

But the top brass at Warner Bros. (distributor of the 1939 film) were not beguiled by this beauty. Instigating a stoush that may have far-reaching implications for how film copyright law is enforced and understood, Warner’s lawyers have scoured every frame for ammunition that could be used to blow away the Big Mouse, then sip champagne while eating his cheese.

Absurd though it may sound, one of the reasons the opening of Oz: The Great and Powerful was legally cleared is because use of black and white cinematography is not against the law. A judgement call was made that the same could not be said about — wait for it — the film’s use of shades of the colour green.

Author Frank Baum wrote The Wonderful Wizard of Oz, a children’s novel, in 1900. This means characters such as Dorothy, the Lion and the Scarecrow exist within public domain. But the 1939 production adds elements the book does not have. And here’s where it gets tricky.

In 2006 Warner Bros sued a company named AVELA, which specialises in nostalgia merchandise (like, for example, Tin Man t-shirts with captions such as “If I only had a heart”). Five years later the case ended up in the Eighth Circuit Court of Appeals, which ruled that properties associated with characters can be copyrighted even if the characters themselves cannot:

“There is no evidence that one would be able to visualize the distinctive details of, for example, Clark Gable’s performance before watching the movie Gone with the Wind, even if one had read the book beforehand. At the very least, the scope of the film copyrights covers all visual depictions of the film characters at issue, except for any aspects of the characters that were injected into the public domain by the publicity materials.”

Therefore, depicting Dorothy’s iconic red shoes was never on the cards for Sam Raimi (they were silver in Baum’s book). Munchkins still exist in Oz: the Great and Powerful, but Disney lawyers deemed some of their haircuts too close to ones in the original film. These were restyled in post-production.

If you thought that sounds a tad pedantic, it gets worse.

Oscar-winning makeup artist Howard Berger, assigned the task of turning Mila Kunis into the new Wicked Witch of the West, “was finally able to come up with a shade of green which satisfied Disney’s legal team,” according to a report published on SlashFilm.com.

Unusual copyright issues such as the ones highlighted by Warner Bros.’ aggressive protection of the Oz universe are not unprecedented.

In 1978, the American government redefined public domain regulation, extending copyright expiration for works created between 1923 and 1977. For the Sherlock Holmes universe, this means Conan Doyle books published before that period exist in the public domain, but stories in ‘The Case Book of Sherlock Holmes’, published in America in 1927, are protected by copyright until 2023.

So while you can legally create original stories set in the Sherlock Holmes universe, these stories could contravene copyright regulation if they reference components unique to the 1927 book.

But avoiding breaking the law by changing the shade of the colour of a representation of a character that exists in the public domain is on a whole other level.

In the context of an escapist fantasy intended to transport viewers to a rainbow coloured parallel dream world, this is the ultimate reality check. No matter how many times Dorothy clicks her heels, she’d better be certain “there’s no place like home” doesn’t have a TM looming after it and that her friendly Munchkins have lawyered up. Behind the scenes machinations are as brutal as they are banal.

As the original The Wizard of Oz suggested, if you want to get swept away in the transformative powers of illusion, magic, cinema, etcetera, it’s best not to look behind the curtains.