You've received an offer from a law school, you applied for a deferral, and it's been granted. Woohoo! Right? Oh wait. There are conditions. Uh-oh.
People apply for deferrals for lots of reasons. Maybe you want to pursue a one-year fellowship before you start law school, or you just got a promotion at work that you think will be a formative experience, or you have a once-in-a-lifetime travel opportunity (post-Covid, knock on wood), or you want to hold your spot and see where else you might get in if you retake the LSAT. A deferral allows you to hold your spot at a school and push your start date off by a year, so that sounds like the perfect solution.
Not so fast. If a school grants you a deferral — and that's not a given — then you might be asked to sign a deferral agreement promising that
you will withdraw all your other applications (so no more pending waitlists)
you won't be in deferral status at another law school
you won't apply to other law schools in the deferral period
you will resurface by a certain date to reaffirm your intention to matriculate the following year
The specific language might vary, but the terms are usually unambiguous. If you sign that agreement and don't abide by its terms, for example by staying on waitlists elsewhere, then they can yank your offer. Some law school applications even ask if you have signed a deferral agreement elsewhere. If you violate the terms, you can be blackballed by the other schools to which you have applied (or were planning on applying). You might find yourself with no offers whatsoever.
Not all law schools impose these conditions on deferrals, so you have to read the deferral agreement carefully. (Note too that law schools typically won’t grant any deferrals from an offer made from a waitlist — that’s because they’re trying to fill those spots quickly for the upcoming academic year.)
So by all means sign the deferral agreement if you want a school to hold your spot for a year while you do great things (other than applying to more law schools). But don't sign it if you don't like its terms. If you try to game the system, the system might bite back. You're always free to reapply later if this isn't the right time to go, or if you want to keep all your options open.
P.S. What if you change your mind entirely and decide during the deferral period that this whole law school thing isn't for you? That happens too, and that doesn't violate the deferral rules. You'll just lose your spot when you don't reaffirm your interest in matriculating, but you'll be doing a courtesy to people who do really want to go there if you release your spot sooner rather than later.