Fideicommissorum libri
Ex libro XII
The Same, Trusts, Book XII. When the ownership of property is not in controversy, but the usufruct of the same is (for it may happen that the ownership is bequeathed to Titius, and the usufruct to someone else), then security to restore it should not be given to the heir, but to Titius. Sometimes, even if the heir is charged with the transfer of the usufruct, security should be given to Titius; for instance, if the usufruct, having been reserved, the ownership is left to him, and the usufruct to Seius; for, in this instance, what advantage would it be for security to be given to the heir, since no benefit will accrue to him if the usufruct should be extinguished? If, however, the usufruct, having been bequeathed to Seius, and the ownership is left to Titius in such a way that when the usufruct ceases to belong to Seius, he will be entitled to the ownership, then security must be furnished to the heir by the usufructuary, and also by the heir to Titius, because it is not certain that, if the usufruct should be extinguished, the ownership will be acquired by Titius.
Marcianus, Trusts, Book XII. There is no doubt that property can be left in trust to a municipality. If security should not be provided, we have no hesitation in saying that, according to the Edict, the citizens of the town can be placed in possession of the estate; but they themselves, if security should not be given them, cannot be placed in possession, but an extraordinary remedy will be required; that is to say, an agent who represents them can be placed in possession of the property by a decree of the Prætor.