M.Mouse
I had a similar one, but on a transit, ( pre - ACARS ) but the on board C.C. had mis-interpreted their own rules, which were related to departure ex-UK, not downline disruption. Eventually used the P.A. to explain and ended by saying that the Flt. Crew were prepared to continue to original destination if the C.C. would accompany them ! Collapse of Stout Party.
Of course I was reported to the then T.U.C. for coercing people to work, but I was right in my interpretation of their rules, so that was OK.
( longer story of course, and the situation had arisen because Control Centre had fooled them into departing LHR with a downline promise of relief that they eventually couldn't come up with, I felt sorry for the C.C. but the show went on and no rules were broken )
Best of luck in the coming few days. ( or years ! )