There is a legal phrase "without let or hindrance".
The word "let" seems peculiar, and actually opposite to the usual meaning.
Looking for the origin of this particular useage. Is it, perhaps, a separate word that is only coincidentally the same spelling? Is it ever used in this sense outside of that specific phrase.?
It's "let" as a noun. Two dictionaries with that example:
AHD let
let (2) noun 1. Something that hinders; an obstacle:
free to investigate without let or hindrance.
It's also in Merriam-Webster:
M-W let
: something that impedes : obstruction
ruled his little world without hindrance or let—
"Let" as that noun has its own etymology:
etymonline let
The link says it's obsolete except in legal contexts.
That makes it a homograph of other senses of "let".
