The wall painting shows a judge in a traditional wig who with his club hits a demonstrator with a bloody placard.
The painting, which is seen as a reaction to the arrest on Saturday of several hundred demonstrators who support the banned group Palestine Act, was quickly covered with black plastic and metal barriers. It was guarded during the day by security guards, writes the British media.
Banksy shared at the same time a photo of the wall art on his Instagram account with the image text "Royal Courts Of Justice. London."
The British government recently banned Palestine Act under anti-terror legislation.
