Actually it's like magic where they went to tap their land to attack but in response SoF destroyed the land and so they couldn't. Duh.

Edit: Oh but seriously, no doubt there was more of qz's blathering about pact terms that was not included in Chevs post. They didn't have to break a pact, because they have a voiding clause built in for FDPs which SoL is one of them (according to slagpit). On top of that, Chevs gave his blessing and voided it before they could so everyone could save face and not have the fluffstorm LaF created from actually breaking a real pact despite not meeting the void criteria.

Just a guess, but I'd bet money on it.