The Justice Department (JD) was founded in the United Kingdom by animal rights activists who declared they were willing to use a diversity of tactics up to and including violence against their opponents. Initially calling for "abusers to have but a taste of the fear and anguish their victims suffer on a daily basis", activists established a separate idea from adhering to the Animal Liberation Front's (ALF) guidelines of non-violent resistance, similar to that of the Animal Rights Militia (ARM).

The first recorded action took place during Christmas 1993, when pipe bombs in poster tubes were sent to Shamrock Farm, a supplier of primates for animal experimentation. The group had formed the same leaderless-resistance model as the ALF, which consists of small, autonomous, covert cells acting independently. Members of the Justice Department are thought to be both supporters of the far-right and the far-left who engage in a common interest, which is animal rights.

The name has also been used in the United States with activists claiming hundreds of attacks in the UK against animal testing companies, their suppliers, animal researchers, hunters (including the Royal Family), and even the British National Party HQ. By sending explosive devices and razor blades in the post, and leaving incendiary devices on shelves, The Independent labeled the political violence "the most sustained and sophisticated bombing campaign in mainland Britain since the IRA was at its height." with the FBI declaring them to be "the most dangerous animal activists in operation".