Forum:T.G. HALBERD CANNON

T.G. HALBERD CANNON ATK/4000 DEF/4000

Effect: 1 Tuner Synchro Monster + 2 or more non-Tuner Synchro Monsters This card cannot be Special Summoned except by Synchro Summon. Once per turn, while this card is face-up on the field, you can negate the Summon of a monster and destroy it. When this card is sent from the field to the Graveyard, you can select 1 "T.G." monster in your Graveyard, and Special Summon it.

Question?

The effect of negating summon this monster can be activated on opponent's turn?

Or just turn on your own?