@WolfishMusings
I haven’t read through every post here, but I am very disappointed at the quality of response to answer your simple and legitimate question.
(My feeling is that it falls into the category of a mitzvah for them to comply, just as Rambam counts it as a mitzvah for Beis Din to administer misah, or any court consequence. So, whatever recourse they have to enforce any mitzvah, applies here too – I just don’t know what that is. Or if they don’t comply, perhaps beis din won’t force them at all, and that’s just their aveirah between them and Shomayim, and being that the possukim go on to allow others to finish off the sentence after them, beis din will just resort to that now too.)
Let me know once you find an answer.