Like the Vienna Convention, this book is concerned primarily with treaties between states. Article 2(1)(a) defines a ‘treaty’ as:

As with most of the Convention, although the definition is expressed to be for the purposes of that Convention, and is limited to treaties between states, its elements now represent customary international law (see previous chapter). As with so many legal questions, the difficulty is not the definition itself, but whether a particular instrument or transaction falls within it. An examination of the elements of the definition illustrates some of the key principles underlying the law of treaties.

But, first a warning. The law of treaties is extremely flexible and can accommodate departures from normal practice. That is its strength. But most treaties are drafted according to standard forms and processed according to long-established procedures. One should therefore think very carefully before departing from them. But, provided there is a good reason for a departure, and one knows exactly what one is doing and any legal implications, there should be no problem. Difficulties can arise when there is an honest, but misguided, wish to speed up the process; the initiative often coming from the state promoting the negotiation of a multilateral treaty.