Since President Woodrow Wilson issued this sincere, but unworldly, appeal in 1919, diplomacy has continued to develop many new ways of doing business. Diplomats know that it is impossible for all international deals, whether important or not, to be embodied in treaties, even when the matter is proper and lawful. Hence the relentless rise of the MOU. As described briefly in the previous chapter, an MOU is an instrument concluded between states which they do not intend to be governed by international law (or any other law) and, consequently, is not legally binding.

But first, a word of warning. Because the use of MOUs is now so widespread, some officials may see the MOU as the norm, a treaty being used only when it cannot be avoided. The very word ‘treaty’ may conjure up some of the more fearsome formalities of diplomacy. One of the tasks of legal advisers is to explain the differences between a treaty and an MOU, and why one might be preferable to the other. In general, unless there is a particular advantage in having an MOU, such as confidentiality, there should be no reason to avoid having a treaty. Equally, in principle, there is no reason to prefer a treaty to an MOU unless there is a need to create legally binding rights and obligations or, given the subject, there is a constitutional or other domestic legal requirement for a treaty.