Geller and Spencer were leaders in the movement to stop the construction of a mosque near the site of the Sept. 11, 2001, terrorist attack in New York City. A Norwegian man who murdered 77 people, most of them children, in 2011 cited Geller as a source of inspiration.
Geller and Spencer have condemned the attack and say Great Britain was standing against freedom of speech.
"In not allowing us into the country solely because of our true and accurate statements about Islam," Geller said, "the British government is behaving like a de facto Islamic state. The nation that gave the world the Magna Carta is dead."