Preface: The ruling of breaking the bones of the deceased
It is haram to break the bones of the deceased. This is by agreement of the four schools of jurisprudence.
Firstly: Disentombing the Graves of the Muslim
It is haram to disentomb the graves of the Muslims without a legal justification. This is by agreement of the four schools of jurisprudence.
Secondly: Disentombing the Graves of the Disbelievers
1. The graves of the warring disbelievers
It is permissible to disentomb the graves of warring disbelievers in order to use its land for what is beneficial for the Muslims, like a mosque or otherwise. This is the position of the majority: Hanafis, Shafi`is, and Hanbalis.
2. Disentombing the graves of the legally contracted
It is haram to disentomb the legally contracted in the state. This is explicitly mentioned by the Hanafis, Hanbalis, and Ibn Battal from the Malikis.
Thirdly: Disentombing a Grave if Wealth was Forgotten Therein
It is permissible to disentomb a grave if there has been some wealth left in it by mistake, like a ring for example. This is by agreement of the four schools of jurisprudence.
Fourthly: Disentombing when the Deceased is Buried Without Being Washed
Scholars have differed over whether to disentomb a deceased buried without being washed or not, and this is according to two views:
The first: is that the deceased is disentombed and washed if he is yet to decompose. This is the position of the majority: Malikis, Shafi`is, Hanbalis, and a position among Zahiris.
The second: is that he is not disentombed despite having not been washed. This is the position of the Hanafis, Ashhab from the Malikis, a position among Shafi`is, and a narration from Ahmad.