Fideicommissum, in the Civil Law, was a conveyance of property in trust to be transferred to a third person named by the trustor. Fidicommissa, when first introduced, were not supported by the law. The performance of them depended, therefore, on the conscience of the party intrusted, and consequently they were frequently not carried out. They were originally adopted for the purpose of conveying property either where a party, from the circumstances of the case, as inability to procure the proper number of witnesses, was prevented from executing a will, or where he desired to benefit those who by law were precluded from taking the property. To effect this purpose an actual conveyance was made to a friend, coupled with a request that the property should be transferred to another. Fideicommissa, having thus been introduced for a special purpose, were by degrees extended to conveyances of the whole inheritance, and finally were used for the purpose of settling estates in a particular order of succession, forming the earliest instance of Entails (q.v.). Fideicommissa first received the sanction of positive law in the reign of Augustus, by whom authority was given to enforce the performance of these fiduciary obligations. A special prætor was afterwards appointed for the enforcement of trusts, and the Emperor Claudius subsequently extended this authority to the consuls and presidents of provinces. Fideicommissa were either particular or universal, the former being a bequest of a particular subject, or a part only of the inheritance; the latter comprehended the whole estate. The Senatus-Consultum Trebellianum enabled a person profiting by a universal succession of this kind to sue or be sued as heir.
In Holland the principles of the civil law as to fideicommissa form an important branch of the law in regard to landed estates. An heir may be required to transfer either the whole or a portion of his inheritance. The provisions of the Senatus-Consultum Trebellianum also have been adopted. Children who have received their legal portions, and are required to transfer to a stranger the rest of the inheritance, are entitled to retain a fourth part for themselves. Similar provision may be found in the legislation of other countries which follow the civil law. See Hunter's Roman Law, and the Dutch and German manuals of Civil Law.