Unfortunately it seems that religion and belief are often immune from legal protocol. The idea being promoted here, that JW-cult activities are voluntary is on the surface so very true. But when there are generations of your family in the cult, the truth becomes very blurred. If you have never known anything else then the cult is your world and these "voluntary" activities become compulsory. By not undertaking them you are castigated by the reality that you have always known, your life-long friends and your relatves including those closest to you, see you as something unclean and detestible, they see you as a danger. They will shun you inorder for you to "come your senses", this is emotionally draining and often you you have no choice but to capitulate and start following the rules again. The prison may be self contained but the many the cost of walking away is just too high.
Is WT Violating International Law?
Withholding "privileges" is not really violating anything--any more than withholding benefits of membership in a club after a person quits the club.
However, they do initiate the use of force, threats of force, and fraud to get and keep people into the cancer. They threaten with death unless people are doing all they possibly can, and then some, to promote the message. They hold back vital information from prospective recruits, and then hold them to obeying the rules as they pop up. They bust up families when one member leaves the cancer (which is not a "privilege", but a right). They threaten people with destruction if they break one of the many rules. They harass people that leave the cancer, and they continually harass the public threatening them with death and destruction unless they join. And that is enough to get them banned.
As for the poster that claimed that you can leave at any time, it is technically true. However, the witlesses program people (especially those who were born in) to fail outside the cancer, so they have to return. Additionally, they bust up families, cut off all association with those who choose to leave, and do whatever they can to sabotage people's chances of succeeding outside the cancer. After being cut off from the world, people that leave are cut off from the religion, leaving them with nothing. Often, they are set up so housing and employment are contingent on staying in--they will have a witless boss or contracts that are all witlesses, and/or a landlord slum lord that is a witless that will happily terminate your contracts, employment, or lease if you leave the religion.
Effectively, this forces many who are in the cancer to stay in the cancer.