Warp Spiders and Obliterators
Quick rules question. I was playing in a tournament and my opponent targeted a squad of warp spiders with their assault cannons. I made a jump and moved out of range. He then claimed that he could pick another weapon system to fire at them with since the rule stated the firing unit cannot pick another unit to shoot at, but nothing about picking a different weapon. That seems wrong to me, I think it goes
Declare weapon choice > check range > spiders can jump > check range > resolve attack
Declare weapon choice > check range > spiders can jump > declare weapon choice > check range > resolve attack
credit goes to wolf.