Two interns who completed unpaid work on the Oscar-winning film Black Swan have won a landmark case against the studio behind the movie, 20th Century Fox.

Alexander Footman and Eric Glatt had complained they were made to undertake menial work with little or no educational value that ought to have been carried out by paid employees. US law makes it clear that unpaid interns must gain educational benefit from their work experience and cannot be used to replace regular paid workers. Federal judge William Pauley ruled yesterday that Footman and Glatt were in fact "employees" of studio offshoot Fox Searchlight, which oversaw production of Black Swan, meaning they were entitled to legal protection under minimum wage and overtime laws. The judge also dismissed suggestions by Fox that the interns were working for Darren Aronofsky's production company, rather than directly for the studio. Finally, Judge Pauley confirmed he would certify a class action that will explore internships throughout the corporate departments at Fox.

"Considering the totality of the circumstances, Glatt and Footman were classified improperly as unpaid interns and are 'employees' covered by the FLSA and NYLL," said the judge, according to the Hollywood Reporter. "They worked as paid employees work, providing an immediate advantage to their employer and performed low-level tasks not requiring specialised training. The benefits they may have received – such as the knowledge of how a production or accounting office functions or references for future jobs – are the results of simply having worked as any other employee works, not of internships designed to be uniquely educational to the interns and of little utility to the employer.

"They received nothing approximating the education they would receive in an academic setting or vocational school. This is a far cry from [the supreme court's decision in] Walling, where trainees impeded the regular business of the employer, worked only in their own interest and provided no advantage to the employer. Glatt and Footman do not fall within the narrow 'trainee' exception to the FLSA's broad coverage."

However, another intern who worked on the Fox film 500 Days of Summer was stymied in her attempts to sue. Judge Pauley accepted the studio's assertion that Kanene Gratts' claims were time-barred.

Fox said it would fight to overturn the ruling. "We are very disappointed with the court's rulings," the studio said in a statement. "We believe they are erroneous, and will seek to have them reversed by the second circuit as quickly as possible." The studio had previously said it changed its guidelines in July 2010 to ensure that all interns are paid at least $8 an hour.

Black Swan earned more than $300m (£191m) at the global box office and won the best actress Oscar for its star Natalie Portman in 2011.