The problem here, as I see it, is abuse of power by the state.
The boy lives with his mother. He has the permission of his mother to ordain. About the father nothing is said.
It was an uncle of the boy (a brother of the mother of the boy) who saw a documentary with the boy about his intention to ordain, and then this uncle hired a lawyer and contacted the police and the Child Welfare Service. There were disputes between the mother of the boy and his uncle in the past already, and it looks very much like the uncle deliberately wants to create problems for the mother and the boy. He says the boy was brainwashed by his mother and raised too isolated.
Therefore, earlier this week, a juvenile judge saw the boy and concluded there are no reasons to hold the boy in Belgium; he was allowed to go to India and ordain.
Last friday, 15 minutes before the mother and the boy would depart for the airport, 3 police cars and 6 police officers came to the house of the boy and escorted him to a court of justice where he heard from a judge that he was not allowed to leave the country. The prosecutor had lodged an appeal.
My opinion is, that if the parents agree, and that if the boy really wants it, and a juvenile judge made a judgement and says everything is ok, it is abuse of power by the state to forbid people to leave the country. It's something that happens in a dictatorial state or in a police state.
This is the monastery the boy wants to join: http://www.jonangmonasteryshimla.com/
“Look on the world as empty, Mogharāja, being always mindful.
Having removed wrong view of self, in this way one will cross beyond Death.
When looking on the world in this way the king of Death does not see one.” - Sn 5.15