General warrants, which were usually issued in secret in London, permitted British soldiers and agents in America to search wherever they wished and seize whatever they found. General warrants were not based upon any individualized suspicion, much less any probable cause. Their stated purpose was the need to enforce the Stamp Act, a totalitarian measure that cost more to enforce than it generated in revenue.
Source: The Fourth Amendment Is Supposed to Work for the People, Not the Government – Reason.com