In a recent game, the Targaryen player used Astapor to power up one of his Dragons. The Stark player responded by kneeling an influence to move Freezing Rain onto Astapor. An argument then ensued. The Targ player said that the power-up effect was already on his dragon and couldn't be removed. The Stark player said that the power-up effect, though on the dragon, only existed because it was defined by Astapor, which was now blanked and therefore void.
Who would be correct in this?