Hi, Consider a model with Guard entering ZOC of an enemy troopers on it's first move, but not reaching base contact. Can that Trooper declare CC in ARO? If so, what happens if the Trooper with Guard does not declare CC? Same question applies when entering ZOC of an enemy trooper with Guard. Can you declare CC on you first short skill, knowing that the Guard Trooper can respond with a CC ARO? Or are you only allowed to declare CC if the target declared CC in ARO?
You can in both cases as requirements for skills are checked after everything is declared in the Order Expenditure Sequence, but if the trooper with Guard declares any other skill your CC Attack will be invalid and revert to an Idle.
I'd note that if you examine the rules surrounding Guard very very closely, they are kind of messed up. Not only does Guard represent one of few remaining declaration baits / gotchas that CB's been eliminating fervently the past year, but Guard has a requirement that only applies to the target which is really really weird. I'm not even sure that's technically handled by the rules. Without this requirement, your opponent would be able to CC Attack you if you got your Guard inside LOF and ZOC regardless of your second skill declaration, unless you informed your opponent that you choose to not use the skill, which honestly would be kinda fair and in line with the trajectory CB's been on with removing pure gotcha stuff like this.
