There was a popular challenge in the Harry Potter fandom, back years and years ago before the books had even all been published, called the Marriage Law challenge. Premise: after the war was over, the Ministry declared that the Wizarding world had had too many deaths and they needed more babies and so required people to get married. (This challenge was especially popular in the small but dedicated group of Snape/Hermione shippers.) I was never active in the Harry Potter fandom, but I did read some of the fic and lurked occasionally, and my basic assumption upon seeing "Marriage Laws" as a category would be something similar to that old HP challenge.

OTOH, that was a long time ago, so I have no idea if anybody but me would have that confusion.