According to the EFE news agency, the commission reviewed the video in response to a request for clearance by the television station Telemadrid.
The video, which is part of the PACMA animal rights party's campaign for the European elections on May 25, includes a series of images meant to depict cruelty toward animals, including bullfighting and a photograph of the king and another hunter posing in front of a dead elephant.
The electoral commission said that "under no circumstances" could the image of the head of state be used as part of an electoral campaign.
King Juan Carlos was forced to apologize to Spaniards after a fall which broke his hip had forced the monarch to reveal that he had been on an elephant-hunting safari in Botswana before flying back to Spain for treatment.
He later resigned as honorary president of the Spanish branch of the WWF wildlife conservation organisation after an online petition had called for such a step.
The president of PACMA, Silvia Barquero, told the Europa Press news agency that her party would appeal against the decision.
PACMA, which is campaigning for greater ethics in public life as well as better treatment for animals, gained 100,000 votes in Spain’s 2011 congressional election.