Australian imports the Mongols bring a new level of violence to local streets, police say.
Mongol bike gang members will no longer be allowed to set foot in schools, courts and other government buildings while wearing their patches under a new ban.
The new law comes into effect today.
The Mongols are the second outlaw club hit with the ban; the Comancheros were also banned in 2018.
The Mongols - who have links to Australia and the United States - are believed to have about 20 patched members in New Zealand under the leadership of a 28-year-old man deported from Australia in 2018.
They are also believed to have been involved in a violent Bay of Plenty turf war against the Mongrel Mob in January, using semi-automatic weapons in tit-for-tat shootings and engaging in suspected arson.
Police had earlier warned that the Mongols and other Australian newcomers - such as the Comancheros and Rebels - would radically change New Zealand's criminal landscape, as they brought hardened gang warfare experience with them.
Police Minister Stuart Nash said authorities would hit the Mongols Motorcycle Club - considered by Australian law enforcement to be one of the five worst outlaw motorcycle groups in that country - head on.
"Australian-based gangs like the Rebels MC first started arriving in 2008 and soon became well-established," Nash said.
"Since 2015, more than more than 1800 offenders have been deported from Australia. They are bringing a level of professional organisation and business skills to the meth trade which has not been seen before."
The gang also took part in other serious criminal activity that included supplying and distributing illicit drugs and violent assaults, blackmail and extortion.
The ban came in response to police advice the Mongols MC patches helped it engage in criminal activity and promote and encourage others to join them, Nash said.
"Gang insignia is intended to intimidate the public and other gangs. It is designed to claim ownership of a physical space and to encourage the recruitment of gang prospects."
"We will not allow the Mongols MC to advertise its presence in this way."
Under the law, the Mongols would not be able to show their insignia in any government premises including courts, Work and Income offices, libraries, schools, public hospitals, some sports grounds and public swimming pools.
"Restricting the display of gang patches, by itself, will not prevent the harm caused by organised crime groups, which include white-collar offenders with links to gangs," Nash said.
"However, when combined with other initiatives, such as tougher penalties for gun crime, asset seizures, and more cops on the front line, it contributes to a safer community."
Police have seized cash and assets worth more than $100 million from gangs since 2017.
A dedicated police Gang Focus Unit in Hawke's Bay had also arrested more than 100 gang members or associates in its first six months.
Police had also seized almost 2400 illegal firearms from gangs and other offenders in the past year.
Frontline police numbers also rose 10,085, a jump of about 1250 officers, since the start of the 2017/18 financial year, Nash said.
• Anyone with information about gangs, drugs or firearms can phone the 105 police number or phone Crimestoppers anonymously on 0800 555 111.
The 19-year-old was found in a remote area in the hills of Upper Hutt.