This question already has an answer here:
In GOF the Tri-Wizard cup was a port key that takes Harry to the graveyard with Voldemort.
Aside from the fact that it then takes him back to Hogwarts when he did so he used the Accio spell to bring the cup to him in the graveyard.
Assuming that this shouldnt be possible during the tournemant otherwise any one of the participants could have simply used the spell to instantly win the Cup.
How did this then work in the graveyard ?