Me and my friend like to play the card game yugioh. We always fight over this one rule. I have the legal version of obelisk the tormentor when I have my 3 monsters on the field and say I'm tributing these monsters for obelisk can my friend activate compulsory cannon on one of my sacrifices. One of obelisks affects is you can't negate the summon so can my friend activate this card or no?