The Stormtrooper outfits are popular with collectors
Director George Lucas's production company has lost the latest round in a legal battle against a prop designer who sells replica Star Wars costumes.
The Court of Appeal rejected claims by Lucasfilm that Andrew Ainsworth, who created the original Stormtrooper suits and helmets, was breaching copyright.
It ruled that the helmets were not works of art and were therefore not covered by copyright law in the UK.
The decision allows Mr Ainsworth to continue producing the uniforms.
The court was upholding a ruling made last year by the High Court in the multimillion pound battle over the replica uniforms, which Mr Ainsworth sells online.
The judges also refused to enforce a $20 million (£12.4m) damages award Lucasfilm won against Mr Ainsworth in a US court in 2006, saying the prop designer's US sales were not significant enough to make him susceptible to US jurisdiction.
However they agreed that Mr Ainsworth was in breach of Mr Lucas's US copyright and warned him against seeking "any further selling into the US".
According to the Daily Telegraph, Mr Lucas intends to appeal the decision.
'Entitled to protection'
A spokesman for Lucasfilm told the newspaper: "This ruling deals a significant blow to the copyright protection afforded not only to Star Wars but to every other great success of the cinematic arts, from Harry Potter to Dr Who and beyond."
Mr Ainsworth was paid £35 for each helmet he made for the film in 1976
Mark Owen, from law firm Harbottle and Lewis, which acted for Lucasfilm said: "To say that you cannot retain copyright unless the object in question is by a renowned artist just seems wrong. Why should people be able to copy something?
The ruling is the latest twist in the legal battle which has been running since 2004 when Lucasfilm - which owns the Star Wars brand - first discovered Mr Ainsworth was selling the replica outfits.
The designer, from Twickenham, south-west London, was paid £35 each for making the 50 Stormtrooper helmets for Star Wars in 1976.
Nearly 30 years later he found one of the original helmets in a cupboard at his home and sold it to a collector.
He then began using the original moulds to produce more, along with full suits, to sell through his company, Shepperton Design Studios, for up to £1,800 each.