The legal systems of the World have difficulties in harmonising their general contract laws. One major obstacle is the approach to the requirement of good faith or contractual loyalty. The theoretical explanations or foundations of this requirement differ strongly between the legal systems. Here, it is suggested that a way around the obstacle is to explain the existence of the requirement with contractual proportionality.
Munukka, Jori, Harmonisation of Contract Law: In Search of a Solution to the Good Faith Problem (November 1, 2017). in: Perspectives on Jurisprudence: Essays in Honor of Jes Bjarup, pp 229-250, 2005, Stockholm Institute for Scandinavian Law; ISBN: 91-85142-62-X.