In general in statutes, the word “shall” is mandatory, and the word “may” is permissive but not mandatory (but there are exceptions). That is, if you “shall” do something, that means you must do it the way the statute says; you have no options or discretion. If you “may” do something, it is an option, but there could be other options. There are some unique situations where the courts will find “shall” to be permissive, or find “may” to be more like “shall” than one might think, but they are rare. See Eby v. Kozarek, 153 Wis. 2d 75, 80-81, 450 N.W.2d 249 (1990).
As I’ve pointed out before in this blog, deadlines are one area of the law where there is very little discretion. When Mr. Sherard was found guilty in Milwaukee’s municipal court of a number of building code violations and fined roughly $10,000, he had 20 days to file an appeal. He missed the deadline. But he filed an appeal anyway. He argued that the “shall” appeal within 20 days found in Wis. Stat. § 800.14(1) was not meant to be a hard deadline, but an option. The circuit court did not buy the argument, and found “shall” to be mandatory. If you don’t file on time, you almost certainly lose no matter what the merits of your case may be. City of Milwaukee v. Sherard.