In fact it depends a lot on the legislation of the country in question.
In France we had a huge controversy with the succession of singer Johnny Hallyday. (his children were disinherited by testament written on the territory of the United States)
Vanessa has reason about French legislation :
Our civil code imposes an "incompressible reserve" for benefit children of the heirs. The proportion of this "reserve" increases according to the number of children who can be called to the succession.
The rest of the estate is called "available quota" and can be redistributed according to the will of the author of the will. Without a will, the whole will be returned to the children (except in case of life insurance established in the name of a foreign person)
And it is indeed possible to squander the fortune during his life but the heirs however can take legal action to counter expenses where donations totally disproportionate which can put in danger the part of the inheritance of the children (Case Liliane Bettencourt)
There are also cases of "unworthiness" for which a child may be excluded from the estate. But these are very rare cases (to attack the life of the legante, to have brought against him serious slanderous accusation ...)
However, I could not speak for other countries because I only studied French law at university.
If not in France the fact of forcing a minor to wear a chastity belt (against his consent) would be recognized by the courts as an act of child abuse: https://fr.wikipedia.org/wiki/Maltraitance_sur_mineur
Heading: Psychological / Emotional Abuse
In France the judges would have very heavy hand compared to this kind of case. The minor child would be in my opinion placed in a home with psychological follow-up. The parents would be sentenced to prison (but with execution suspended).
Once the majority (18 years) reached by child, the parents would be more difficult to attack but they could however be called to answer for their actions especially if the person of age did not have sufficient discernment to undergo such a constraint.
Thus even if there has been no case of concrete case-law on specific subject, the French judges would be in phase with the public opinion of the current manners.
The people I had the opportunity to discuss about the forced wearing of the belt were all deeply shocked and nauseated about the behavior of the parents of this forum. None of them told me, "It's good, it's a great way to educate your daughter so she does not become a bad girl later"
It is obvious that the "educational" aspect would not be retained by the French judges and that they would retain "the abuse of parental authority" and "psychological abuse" on the child. I have no doubt about their decision