It has a replica built inside it, CBSA will seize anything that looks like a gun. Hell they sometimes seize mechboxes just cause they have triggers. Paintball guns that look like real guns are like a 90% chance of being seized aswell. (most however you can get eventually by fighting the seizure but that takes so much time/money that it's cheaper to buy in canada)
Also, that specific gun and this exact question have been asked MANY times.
one last point, that gun is ugly as shit.