If you use the shield to block bullets and someone on your team kills the person firing at you...you get crowdd control assist.
This could be partly wrong but this is how I've completed those quests.
Also i think it counts if someone is shooting at enemy but didn't kill them fully and you finish them off with the shield.
Cavalry is a ++++ division anyway so will probably give this order a miss.
I used to absolutely hate domination because I'd always end up in kill whore lobbies but now I enjoy it and that's thanks to this class rewarding the hell out of me for playing the objective AND the occasional rage fit I hear everytime I kill someone with the shield makes my day lol
There's almost no better feeling than after capping a point then charging the jeep lmg score whore and lambasting them with a shield and racking up kingslayer medals😁
It is easy to get and basically if someone is shooting at you and someone else kills them you get the Crowd Control Assist, imagine how easy this is to get on a map like Shipment or a game mode like Domination?