The New Zealand Government has gone into urgency to suspend the effect of the Supreme Court Urewera judgement after it rendered all police video surveillance footage unlawful.
Police said their ability to prosecute drug case could be at risk because of a gap in the law revealed in the Urewera raids case.
Cannabis cases were among those affected by the decision.
"Up to 40 current trials may be affected by this decision and over 50 police operations will be impacted," John Key told a press conference this afternoon.
ALCP Leader Michael Appleby said the Government's disregard for the Supreme Court's ruling was unprecedented.
"They have declared war on the cannabis community as well as the judiciary," he said.
The urgent law change will apply retrospectively so prior convictions in trials in which covert surveillance was used to collect evidence cannot be overturned.