Cases of unfair (or unjustified) enrichment can be examined as follows: in Scotland, the law developed in pieces until the 20th century and peaked in three crucial cases in the late 1990s. The most important of these was Shilliday v Smith, in which Lord Roger essentially laid the foundations for what is now considered a modern Scottish law of unjustified enrichment, by grouping the fragmented law into a framework based on the principles of Roman law on which Scottish law as a whole is based (note that the term “unjustified” is privileged in Scotland “unfairly”). Unjust enrichment is more established as an essential element of compulsory Scottish law than unjust enrichment in English law. In the law of justice, there is unjust enrichment when a person is enriched at the expense of another person in circumstances that deem the law unfair.  If a person is unjustifiably enriched, the law obliges the recipient to return, subject to the defence as well as the change in the position. Responsibility for unjustified enrichment (or not) arises independently of a fault of the recipient. The notion of unjust enrichment can be attributed to Roman law and the maxim that “no one should benefit at the expense of another”: nemo locupletari potest aliena iactura or nemo locupletari debet cum aliena iactura. In general, the mere perception of one advantage by another is not contestant and has no legal consequences. An exception is the receipt of their “unjust” or “unjustified.” The civil and legal systems of the common law have a legal system that offers remedial measures to reverse this enrichment. Parties and courts have been fighting this issue since the 1970s, with some judges agreeing that all other remedies must prevail over unjust enrichment, while others consider it a matter of circumstance. The sheriff found that his failure to pursue a legal remedy for use by roommates (see 28 of the Family Law (Scotland) Act 2006 prevented him from asserting a right to unjust enrichment. Ms. Pert submitted that, in the particular circumstances of her case, there is no such rule.
Unfortunately, the Inner House then indicated that it had also relied on the existence of an agreement between the parties, that it would receive the full proceeds of the sale. If this had been possible, the agreement itself could have been implemented and its existence was therefore fatal to its assertion of unjust enrichment. The complaint was in Pert/McCaffrey  CSIH 5. Ms. Pert had sued her ex-partner McCaffrey after the sale of her condominium. She submitted that he was not entitled to retain a half share of the sale price (which was paid to him by Ms. Pert`s agent in the receivership), as the initial purchase was financed by the sale of a property owned by him. In any event, it did so too late, regardless of the correct basis of its claims.
The appeal had been filed more than five years after the parties separated. Any allegation she could have made against Mr. McCaffrey as a result of a breach of contract or unjust enrichment had therefore been extinguished by order. The coherent concept of unjust enrichment, then appeared in the Justinian code, based on Roman pragmatism with just considerations and moral principles of Greek philosophy.  In the Justinian Code, the provisions were categorized, for example where the applicant had given something or money: A key question is whether claims can be sued on the basis of undue enrichment if a party has other remedies.