The Indonesian Islamist group Hizb ut-Tahrir was banned in Indonesia for "threatening national unity."

That is a very broad criterion — all sorts of organizations could be banned on those grounds. Worse, the criterion is vague and stretchable — one can hardly tell what is forbidden.

The group got a court hearing about this, but the hearing considered only the question of whether the government followed the proper procedure, not whether the group really threatens national unity, or what the line is.

This is not meant to defend Hizb ut-Tahrir. Every Islamist group opposes basic human rights. Nonetheless, its members are entitled to human rights.

The US has a similar problem due to arbitrary designation of "terrorist groups". The government could designate your weekly bridge group as a "terrorist group", and if it prosecutes you for being a member, the prosecutor would not need to prove the group really has anything to do with terrorism.