One of the splinter groups that emerged when the Aum Shinrikyo cult was broken up in the aftermath of the 1995 sarin gas attack on the Tokyo subway has been successful in its legal challenge against the Japanese government's monitoring of its activities.

While people who recall the events of 22 years ago broadly agree that the group poses little direct threat to public safety, they point out that it continues to recruit followers, often on university campuses where young people do not know the name of the cult because the attack happened before they were born.

In response to a petition filed by the "Hikari no Wa" group, which translates as The Circle of Rainbow Light, the Tokyo District Court on Monday ruled that the government could no longer conduct police surveillance of the group or its members under the Act on the Control of Organizations Which Have Committed Acts of Indiscriminate Mass Murder.

The law was passed after Aum Shinrikyo followers carried out a number of attacks in the early 1990s on the orders of founder Shoko Asahara. These included the murder of a member who wanted to leave the cult and the killing of a lawyer who was preparing a compensation case against Aum, along with his wife and infant son.

Sarin gas attack

In the incident for which it became notorious, cult followers released sarin gas on five packed rush-hour trains in Tokyo on the morning of March 20, 1995, killing 13 people, seriously injuring 54 and affecting as many as 6,000 people.

Asahara and 12 of his most senior followers were tried and sentenced to death. Dozens more received prison terms for crimes that included the possession of weapons, manufacturing illegal narcotics and assaults on opponents of the cult.

Within months, Aum Shinrikyo had been stripped of its status as a religious group and was declared bankrupt the following year - although attempts to ban the group outright were defeated due to Japan's constitutional guarantee of the freedom of religion.

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With Asahara in prison, the group split into two factions in 2007.

Hikari no Wa is still headed by Fumihiro Joyu, a former spokesman for Aum, and has around 60 live-in followers and about 100 lay followers. Joyu has stated that the group has "completely discarded the influence of Aum founder Shoko Asahara," but still carries out religious pilgrimages and gives sermons on Buddhism.

The second splinter group is known as Aleph and remains far more circumspect about its membership and activities, apparently because its followers still swear allegiance to Asahara. A similar petition for surveillance of its activities to be halted was dismissed by the Tokyo court.

Rejecting former leader

"Hikari no Wa rejects absolute devotion to sect founder and death-row inmate [Shoko Asahara] and is substantially different in nature from Aleph, which still calls for deep devotion," Presiding Judge Toshiyuki Hayashi said in his ruling. "It is hard to see both groups as belonging to the same organization."

Yet the name of a cult that struck fear into a nation 22 years ago still provokes anger and concern in many here.

Read more: Aum Shinrikyo's victims fear cult's resurgence

"People most definitely think they still pose a danger, particularly to young people who do not know what Aum did in 1995 because it was before they were born," said Makoto Watanabe, an associate professor of communications and media at Hokkaido Bunkyo University.

"Japanese people are very good at forgetting bad things that happen and there is very little media coverage today of Aum or these surviving groups, so not everyone is aware of their history," he told DW.

"A large proportion of Japanese people believe strongly that the government should keep a close eye on both groups, although it is clear that Hikari no Wa has distanced itself from Asahara's doctrines and that Joyu is attempting to help former cult members who have nowhere to turn now."

And while there is little likelihood of either sect attempting an attack as apocalyptic as releasing a nerve gas on subway trains, Watanabe cautions that the descendants of Aum Shinrikyo are actively seeking new members.

"In large universities across Japan, they continue to recruit new members," he said. "They describe themselves as volunteer organizations that provide assistance, but underneath they are the same cult as before."

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Universities' warnings

Authorities at many authorities have issued warnings to students who might be convinced to join such groups, but are not permitted to ban them due to the constitutional provision on religious freedoms.

Robert Dujarric, director of the Institute of Contemporary Asian Studies at the Tokyo campus of Temple University, told DW the possibility of another cult-inspired near-revolution was negligible - but that such groups could always find willing volunteers.

"Anywhere in the world, there will always be small groups that appeal to the disaffected and those outside of society; we see it in the Middle East with 'Islamic State' (IS) finding a steady supply of volunteers," Dujarric said.

"In years gone by, these are the people who would have been attracted to communism, anarchism or any number of other extremist causes, so there will always be a limited number of people who do bad things. And while I don't think Aum poses a threat now, it does pay to be vigilant," he added.