The Roman law background
The Roman law rules on sale and transfer of title can best be divided into implied and express terms in the contract of sale.
Implied terms
By Justinian’s day Roman law had adopted the rule that, when an object was sold, title did not pass to the buyer on delivery unless the price had been paid, the sale was on credit, or the seller had in some way ‘followed the faith’ of the buyer.2 There is considerable doubt whether this rule existed in classical times and, if so, in what shape.3 All that need be said here is that it probably did not exist in this shape; that it was watered down by the exception regarding the buyer’s faith (in fact, the exception appears to absorb the rule); and that by Justinian’s day it was sufficiently well established to feature in his Institutes.
So long as a rule of this sort applied, the seller was adequately protected until payment.
He remained able to vindicate the property from the buyer or from a third party4 until satisfied by payment of the price. The right which he retained in the object sold was dominium rather than a right in rem of any lesser sort. This rule was a rule of law. It did not depend on the terms of the individual contract, although it could, of course, be departed from, notably by words or deeds amounting to ‘following the buyer’s faith’.Express terms
It was open to the seller to introduce into the contract, for his own benefit, an express term to the effect that if the price was not paid within a certain period then the object should be ‘unsold’ (inempta).
This was known as a lex commissoria. It plainly raised the question whether the term suspended the proprietary effects of the sale until payment was made; or whether the sale was perfected but, in the event of non-payment by the buyer, resolved. It also raised the question whether, if the proper interpretation of the term was that it was resolutive, and the term did in fact come into operation, it operated in rem so as to retransfer dominium ipso facto to the seller; or whether it merely gave him a claim in personam against the buyer.Roman law did not arrive at an immediate or unanimous answer to these questions. Sabinus apparently treated the condition ‘unless the price is paid by a certain day the object is to be unsold’ (nisi pecunia intra diem
2 J.Inst.2.1.41: ‘fldem emptoris secutus fuerit’. It should be noted that throughout this essay the concern is with traditio of res nec mancipr, clearly, in the days before Justinian, mancipatio would raise different considerations.
3 See, for instance, G.2.20; D.18.1.19 (Pomponius, 31 ad Quintum Mucium); D. 18.1.53 (Gaius, 28 ad edictum provinciate). M. Kaser, Das romische Privatrecht (Munich, 1971), vol. I, 418, with literature.
4 Subject, of course, to usucapio.
cerium soluta esset inempta res fieret) as suspensive. This emerges from the fact that he took the view that a buyer could not usucapt before he had paid the price.[364] Paul, however, appears to disagree, and Ulpian introduces the title on the lex commissoria in the Digest with the statement that the better view is that it is a resolutive term.[365] The prevailing classical position sems to have been that the term was resolutive (a conventio rather than a condicio). Accordingly, title in the object sold would pass to the buyer in accordance with the normal rules of sale.
What, then, if the condition was realised? That led to a further question, whether the condition should be treated as taking effect in personam or in rem.
The texts give some support for each possibility: so there are texts granting the seller a vindicatio of the object sold, thus indicating that property has reverted to him;[366] [367] and there are also texts which indicate that the seller’s remedy was in personam? There is considerable dispute about which view was taken in classical law.[368]So long as a solvent buyer retains the object, it does not make a great practical difference how the lex commissoria is interpreted, and what kind of action follows from it.[369] But once the object is in the hands of a third party, it plainly makes a crucial difference whether the seller is able to recover the object itself or has merely a claim on the price. For present purposes it does not matter very much which was the received view of the classical jurists. Nor perhaps even what was Justinian’s view. The main point is that a variety of approaches were illustrated in the texts. Lawyers of later periods could choose which line of authority to follow.
The following sections trace the fate of these various possibilities in Scots law, beginning with the institutional writers. It should be noted at the outset that (at least) three different rules are involved. While these overlap, they do need to be kept conceptually distinct. Each has a purpose of its own, even if at first sight there appears to be duplication.
(1) The mutuality rule. In a bilateral contract, one party cannot be compelled to perform his side of the contract unless the other offers to perform his. A seller is therefore not bound to make delivery of the object unless the buyer offers him the price.
(2) The implied term that property will not pass on delivery until payment is made. Because of the mutuality rule, this term is of significance only if the seller delivers the object before he is paid. It then withholds title from the buyer until he has made payment. Security or credit suffices as an alternative to payment.
(3) The lex commissoria. On account of the implied term that property will not pass on delivery to the buyer until payment is made, this term is of significance only if delivery is made but the implied term is inapplicable: in other words, where the seller either accepts security or follows the buyer’s faith, so that property does pass to the buyer.[370] This term provides for its reversion to the seller.