If a condition to bury someone's body wasn't upheld, is one allowed to exhume the body?

Question

A follow up to this recent question "(Why) May a Beit Din refuse to bury a body in order to coerce a man into giving a divorce?" where a Jewish burial society was instructed to not bury the body of a mother whose son is a get-refuser, in order to apply pressure on the man to give the get.

The answer given there (which was accepted) provided a source that this was permitted, and in this particular case it was reported that the man accepted the deal of:
"ONLY if he agreed to grant his wife a get, his mother would be buried."

Unfortunately it is now being reported that this man is reneging on his promise to give a get.

Since the condition for burying his mother wasn't upheld- and as a means of continuing to apply pressure- would it be permissible to exhume the mother's body and punish this man by not re-burying her until he grants a get?
_{(my gut tells me no, but sources that rule one way or the other would be much better)}

Answer 1

The rules of disinterment are quite strict (see SA YD 363:1), dinonline has a good summary. The case you ask about is not part of the list, nor are there any cases of pressuring a family member. A beit din would have to be asked but the "burden of proof" appears much higher than a delayed burial.

Several exceptions to the prohibition are mentioned by the Shulchan Aruch (Yoreh De’ah 363:1). It is permitted to excavate and remove remains for the following reasons:

• If they were buried there without the permission of the landowner. Under such circumstances, it is a mitzvah to do so (see also Birkei Yosef 363).
• If the grave and remains are likely to be damaged by water or sewage backups, by vandalism, and so on, and there are no alternatives to removal that could solve the problem. This was the reason given by Rav Ovadyah Yosef (Yalkut Yosef, Aveilus 32:9) concerning relocating graves in territories that were returned to Egypt under the Camp David accords.
• If the person was buried in one place with the specific intention of later removing his remains to a different site.
• If the remains are being relocated to the Land of Israel, or to the family burial plot (kever avos). See Iggros Moshe (Yoreh De’ah 3, no. 153), who writes that decisions on relocation of a grave can only be taken by the children of the deceased, and not by the general Jewish community. Another reason for permitting the relocation of a grave is when the current position causes damage to other graves (see Eretz Chaim, Yoreh De’ah 364).

The Shulchan Aruch (Yoreh De’ah 364:5) further rules that a grave that causes damage to the public may be removed, even if the burial took place with the consent of the owner of the property.

We learn from this halachah that the imperatives of kevod hameis yield when they unduly impact the rights of the public to access and use of the property. Rav Moshe Feinstein (Shut Iggros Moshe, Yoreh De’ah 3, no. 151) writes that there is room to distinguish between a single grave and an entire cemetery. However, most authorities specify that the law permitting relocation applies not only to a single grave, but even to an entire cemetery (Rav David Oppenheim, cited in end of Shut Chavos Yeir; Shut Rabbi Akiva Eiger, no. 45).

The application of this halachah will depend on how we define damage to the public, and this depends on the particular circumstances and the approach of the specific Posek involved.

See also here.