Carpe Diem: I'm involved in a game where all of my stones but one are behind a prime - the other stone is on my 1 spot, so also can't be moved. I would think the spirit of the rule would mean that my opponent should unblock, but since I haven't collected ALL of my checkers behind his prime, I can see how a literal translation would suggest that he doesn't need to unblock. Does anyone know with certainty how this should be handled?

The same rule is given on Backgammon Galore as "Limitation on primes: You may not build a prime (six consecutive blocks) in front of all of the opponent's checkers; at least one opposing checker must be in front of your prime".

The rule is about building a prime. So if a certain move would inappropriately complete the prime then it is illegal. The rule prevents the move in question.

The rule whose spirit you're suggesting would be about forcing a player to break a prime that's already been made. That's a very different thing and may not actually be possible at the point at which it becomes applicable.

The rule would be have to be something like "If your opponent cannot move and all their pieces behind the prime are stacked on the single point immediately behind then you must open a point within the prime at the first opportunity". This rule would force the given move or small set of moves that break the prime.

This is unlike the prevention rule in several important ways, as can be seen above. The similarity is that they are both concerned with not allowing a prime in their respective contexts.

To be honest I'm not sure what the spirit of the original rule is unless it's to give the trailing player more chances to prevent the prime happening in the first place. Each turn that the leading player cannot close the prime is an opportunity for the trailer to claim that point themself and retain a link, however tenuous, to the forward territory. Once the prime has been made then it's tough buns, they didn't make it.

I think a rule that extended the spirit of the rule as it appears to me would have to ban primes altogether - and that's quite a game changer.