Palestine Action demonstrators may never be able to visit the US or work in education if they take part in this weekend's protest, the Met Police have warned.
The force have said those in attendance risk being arrested under the Terrorism Act.
It comes after three supporters of Palestine Action were the first to be charged under the Act, Scotland Yard has said.
The group was proscribed as a terror organisation last month after an alleged attack on aircraft at RAF Brize Norton.
Two women and a man, who were arrested at a demonstration on July 5 and later charged, are set to appear in court next month.
