Legal-writing tip: "Must" vs. "shall"

I read a recent Illinois Supreme Court opinion (People v. Garstecki) that I believe validates eliminating the word “shall” in legal documents or statutes. The legal writing scholars suggest using “must” instead of “shall” for a mandatory word because “shall has become so corrupted by misuse that it has no firm meaning. It can mean ‘must,’ ‘should,’ ‘will,’ ‘may,’ or ‘is.’ (Joseph Kimble, Lifting the Fog of Legalese, 160 (2006)) If you draft documents that use the word “shall,” you may want to consider changing your approach. Richard C. Wydick in his excellent book Plain English for Lawyers (5th ed. 2005) recommends using these words of authority: "Must” is required to. “Must not” is required not to; is disallowed. “May” has discretion to; is permitted to. “May not” is not permitted to; is disallowed from. “Is entitled to” has a right to. “Should” ought to. “Will” means one of the following: (a) To express a future contingency. (b) In an adhesion contract, to express the strong party’s obligations. (c) In a delicate contract between equals, to express both parties’ obligations.