Not content with imprisoning Burundi’s leading human rights activist, Pierre Claver Mbonimpa, the government has prohibited his colleagues from holding a peaceful demonstration to call for his release.

Mbonimpa, no ordinary activist, was arrested on May 16 after speaking on the radio about allegations that young Burundians were being armed and given military training. He was charged with endangering state security, has been detained for over a month, but has yet to be given a trial date.

A well-known and much-loved public figure, Mbonimpa, 66, has taken huge personal risks to defend the rights of others. He founded the Association for the Protection of Human Rights and Detained Persons (APRODH) after spending time in prison in the 1990s. It has since become the leading human rights group in Burundi.

Civil society groups have campaigned relentlessly for his release. Over the last few weeks, the airwaves and social media have been flooded with messages of solidarity; petitions for his release are circulating around Burundi; and every Friday has been designated “Green Friday” when campaigners ask Burundians to wear green, the color of the country’s prison uniforms, in support of Mbonimpa.

The government has ignored these appeals, but last week went a step further. When activists informed the authorities that they were planning a peaceful protest in support of Mbonimpa, the mayor of Bujumbura blocked it, saying the demonstration “cannot be accepted because it has an insurrectional character” and no one has the right to influence the course of justice. Activists appealed to the minister of interior but he also said no, telling the civil society groups they should let justice do its work instead of “distracting the public.”

The Burundian government has cracked down on public protests and blocked demonstrations several times before. Mbonimpa was harassed and threatened numerous times before his arrest, but refused to let this stand in his way. Other activists and journalists have also been intimidated.

The government’s heavy-handed attempts to stifle criticism should not succeed. Donor governments should speak out against these repressive measures. And we could all wear green on Fridays, in solidarity with Mbonimpa and other Burundian activists.