Fan Popo is suing the censors.

Last winter, 'Mama Rainbow,' the Beijing-based filmmaker's poignant documentary about six Chinese mothers striving to understand their gay and lesbian children, disappeared from major Chinese Web sites. Fan says an employee at one of the sites, 56.com, told him the film was pulled at the behest of the State Administration of Press, Publication, Radio, Film and Television (SAPPRFT) — a claim the censorship body later denied.

On Monday, Fan officially filed a lawsuit against the government branch, alleging they lied about the directive. Fan hopes the suit will help call attention to ongoing efforts to keep gay people and their stories out of film and television and, more broadly, to the state's effort to silence calls for human rights.

"This is about justice," he said in a telephone interview on Wednesday. "I want to find out why they pulled my film."

"The purpose of fighting this case is, on one hand, to raise public awareness about gay groups — that they should enjoy equal rights and they deserve equal treatment," said Fan's lawyer, Wang Zhenyu.  "On the other hand, to demand SAPPRFT stop its improper control on gay subjects."

Wang said he could not find a single SAPPRFT regulation that prohibited "gay subjects" in film, although Chinese censors routinely block LGBT content based on the notion that it is somehow "pornographic" or "obscene."

The lawsuit comes at an interesting time — for two reasons in particular.

First, Fan filed suit just weeks after Chinese authorities approved the release of "Seek McCartney," a Sino-French co-production about the relationship between two men, one Chinese, one French. Breaking the news on social media, the director, Wang Chao, called it "a small step for the film department” and "a big step for the members of the film industry.”

The release of "Seek McCartney" is indeed a step in the right direction, but Fan's lawsuit reminds us that the trend lines are not clear — it is not generally possible in China to depict gay relationships in film and television, just as it remains complicated and risky to push for LGBT rights.

China decriminalized gay sex in the late 1990s, but discrimination persists, as documented in a detailed report by the United Nations Development Program last year. Though some find a measure of freedom and acceptance in China's big cities, many struggle to discuss issues of gender or sexual identity with their families, and that is the theme of Fan's film and  a video produced by the Chinese branch of PFLAG (formerly known as Parents, Families and Friends of Lesbians and Gays) that went viral earlier this year.

Those who work in China's thriving, but often thwarted, gay cinema space never know exactly what they can or can not do, a gray area that makes it difficult to fund and screen their films. "Even a movie passes censorship, it can be pulled at the last minute, right before it hits the cinema," Fan said.

Second, Fan's lawsuit is part of a nascent effort to use the legal system to tackle LGBT issues. In December 2014, a Chinese court ordered a clinic to compensate a man who underwent "gay conversion therapy" to make him straight. Because there is no Chinese law protecting people from discrimination based on their sexual orientation, the case was framed as a commercial matter between the claimant and the clinic.

Fan's case is bolder in that it takes on a powerful state actor. Maya Wang, a Hong Kong-based researcher for Human Rights Watch, said the case could be a "landmark" because it challenges two politically sensitive issues: state censorship and gay rights. Amid an ongoing crackdown on lawyers, it is "encouraging" that the court accepted the case.

Still, she said, the case shows the limits of legal tactics in a country with weak, politicized courts and no laws against anti-gay discrimination: "Fan is challenging SAPPRFT for information about the film's removal, rather than the heart of the matter, which is discrimination itself," she said.

Fan sees it as just another step in the fight for free expression: "On one level, it's a legal issue, on the other it draws attention to censorship and rights."

The English-language edition of Global Times, a government newspaper known for strident nationalism, picked up the story. Others did not. Fan said he talked to a raft of Chinese journalists yesterday, only to hear later that their stories were rejected, his tale of censorship, censored.

Liu Liu reported from Beijing.