[When Liability Attaches to Maḥājir and When It Does Not]

Answer—and Allah grants success: Maḥājir have two states: a state in which liability attaches, and a state in which it does not attach. As for the state in which liability attaches, it is when they are owned; and ownership occurs by building upon them or the like—such as enclosing with fencing. If that is the case, and then the agent sold them and betrayed his partners in some matter, and that became evident, then he is liable; and if he dies leaving property, the heirs must pay the partners their due.
As for the state in which liability does not attach to the maḥājir, it is when the agent sells the maḥjar before building upon it, tilling it, or the like. What he sells in that state—and then betrayal becomes evident—he is not liable for it, nor are his heirs. That is because maḥājir are (mere) rights, and rights are not sold; what is taken as a “price” in exchange for them is not deemed a price, but rather a permission placed in the seller’s hand. If the maḥjar contains trees owned by the partners, such as acacia and the like, that does not confer ownership of the maḥjar itself; only the trees are owned. The seller then owes his partners what they are entitled to from the price of the trees. All that we have mentioned is the implication of the statements of the jurists of the madhhab.
The proof for that is that the default with respect to land is non-ownership; it is owned by cultivation and reclamation—like fallow tracts (al-jarb)—or by building upon it or the like. Selling and buying what is of that kind is valid and permissible.
As for maḥājir of grazing and the runoffs of water and the like, they are not owned by the people of pasture nor by the people of water; rather, they have the right of grazing and the right to water. Grazing in a place is not among the causes of ownership, and likewise the flow of water from a tract of land to a man’s property is not a cause for ownership of that land.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2