And be it further enacted. (8.1) That in all that territory ceded by France to the United States, under the name of Louisiana, which lies north of thirty-six degrees and thirty minutes north latitude, not included within the limits of the state, contemplated by this act, slavery and involuntary servitude, otherwise than in the punishment of crimes, whereof the parties shall have been duly convicted, shall be, and is hereby, forever prohibited: Provided always, That any person escaping into the same, from whom labour or service is lawfully claimed, in any state or territory of the United States, such fugitive may be lawfully reclaimed and conveyed to the person claiming his or her labour or service as aforesaid. (8.2)

APPROVED, March 6, 1820. (9.1)

The closing lines don't really "close" as much as "drop the bombshell of the division of the U.S."

It makes sense in the context. This isn't an argument, and it doesn't need a conclusion. It's a dang law. The language is trim where you'd expect it to go on at length, and the language goes on and on and on where you would expect it to be short and snappy.

The designation of Missouri's geographical boundaries, for example, takes up nearly twenty percent of the whole Compromise. Congress wasn't writing a florid love letter to the people of Missouri: they were writing a highly contentious and potentially disastrous bill that would cement the sovereignty of new states into law.

Any language not strictly necessary for this task was thrown out the window at the outset.