I’ve stated elsewhere (for example, in this 2014 article) the advantages of using shall to express an obligation imposed on the subject of a sentence, if the subject is a party to the contract.
The primary advantage is that shall gives you an extra tool to work with. Instead of using will or must to express multiple meanings, you use shall to express obligations imposed on the subject of the sentence and use will and must for other categories of contract language. That helps you figure out what meaning you wish to express in a given context.
But one of the ancillary advantages is that using shall to express obligations is safe, despite fearmongering to the contrary. (See MSCD 3.60–.61.) For purposes of contracts, court consider that expressing obligations is the foundation meaning of shall.
Recently I encountered an opinion in which a court expressed in a novel way the notion that shall serves to express that which is mandatory. In Vandertoll v. Kentucky, 110 S.W.3d 789, 791 (Ky. 2003) (here), statutory text was at issue. Here’s what the court said:
We will not commence a lengthy discussion on the definition of “shall.” KRS 446.080(4) states that “[a]ll words and phrases shall be construed according to the common and approved usage of language ….” “In common or ordinary parlance, and in its ordinary signification, the term ‘shall’ is a word of command and … must be given a compulsory meaning.” Black’s Law Dictionary 1233 (5th ed.1979). “If the words of the statute are plain and unambiguous, the statute must be applied to those terms without resort to any construction or interpretation.” Terhune v. Commonwealth, Ky.App., 907 S.W.2d 779, 782 (1995) (quoting Kentucky Unemployment Insurance Commission v. Kaco Unemployment Insurance Fund, Inc., Ky.App., 793 S.W.2d 845, 847 (1990)). Shall means shall.
So “shall means shall.” That effectively conveys the impression that the meaning of shall isn’t even worth discussing.
When it comes to the language of statutes, things aren’t so clear cut, because for purposes of statutes there’s the notion that shall can mean “should” (that concept is referred to as the “discretionary” shall.) So perhaps the court in Vandertoll shouldn’t have been so sanguine.
But that court isn’t alone—a search on Westlaw uncovered 102 cases in which the phrase “shall means shall” occurs. So it can be regarded as an oddity that stands for the proposition that courts think that expressing that which is mandatory is the foundation meaning of shall.
Of course, in contracts nothing is certain. See for example this blog post, about how a court held, anomalously, that in a contract dispute a given shall was a discretionary shall. But if you want certainty, don’t do contracts.