This might be a simple question, but I’m curious…as stated in the title, how are borders defined legally? Meaning, do the laws have exact textual descriptions down to every geometric curve and bend, or do the bills that define them include graphical descriptions that carry the force of law, or something else entirely?
For example, how do the oddly-shaped and gerrymandered U.S. congressional districts actually get passed by their state legislatures?
The reason I’m asking is because every example of a passed law I’ve ever seen has been text-only, which seems like a very difficult way of expressing something as complex as what constitutes a congressional district these days. (Maybe there’s an important part of Schoolhouse Rock that I’m missing.)
Nope, the legally controlling instrument is the wording of the statute. As you note, for modern urban congressional districts, these can be quite elaborate.
The use of modern GIS methods to computer-map districts down to individual blocks makes it relatively easy to generate the metes-and-bounds descriptions. Normally they use boundaries that can be seen on the ground, but there are exceptions such as county lines. And sometimes there are curious consequences. Last spring the Chicago city council passed its decennial redistricting ordinance so hurriedly that the wording referred to “unnamed geographic segment such-and-such,” apparently from old TIGER files, and drafters notations such as “don’t you mean to go to the alley to get the big apartment building?” In my neighborhood, the ordinance specified a railroad line torn out 30 years ago, so the ward boundary theoretically would have split people’s living rooms from their bedrooms. A technical corrections ordinance was quietly passed in August to clean up the various messes.
Zoning ordinances are a similar phenomenon. Everyone involved refers to a map to know what a property is zoned, but the actual ordinance will order “the symbols for the area bounded by Prentice St., Allerton Ave., the alley next east of Prentice St., and a line 131.45 feet north of and parallel to Allerton Ave. be changed to those of C3-5, General Commercial District.”
Here’s the law defining Ohio’s new congressional districts. It’s all whole counties, census tracts, and census block groups. There’s also a provision that any area they forgot to name is in the least populous district that it touches.