More weapons are being intercepted at New Zealand's borders but the law limits investigations into those behind importations, Customs says.
Interceptions of weapons and objectionable material have increased in recent years.
Dangerous weapons, including a recent package of stun guns from Hong Kong, are often destined for gangs.
Read more: NZ Customs wants new powers to see passwords
When the New Zealand Customs Service detects an importation of drugs it sometimes - usually with police help - releases the package or goods and tracks them to their destination. This allows the true importer to be identified.
However, under the law, prohibited or restricted weaponry and objectionable material cannot be subject to such a controlled delivery.
Customs has called for that to be remedied in a discussion paper on changes to the Customs and Excise Act.
The paper outlined a number of other changes Customs wants to boost its powers, including requiring a person to provide a password or encryption key to their electronic devices.
Customs' interceptions of prohibited or restricted weapons increased from just over 400 in the 2011/12 financial year to just over 700 in 2013/14.
"As criminal syndicates develop more advanced and complex ways of importing illegal goods, Customs will need to adapt," the paper states.
A recent package arrived in New Zealand from Hong Kong containing 12 stun guns, Customs noted.
Previous seizures of goods destined for the same address contained weapons intended for gang-related activity.
"If a controlled delivery had been used, Customs would have been able to carry out a more thorough investigation and obtain evidence of the actual importer."
On the electronic device proposal, Customs Minister Nicky Wagner said of more than 10 million passengers across our borders in the past year, only about 1500 had their electronic devices examined.
"If you are Joe Bloggs public [the password change] is really of no consequence to you, because you are very unlikely to be 1500 out of 10 million."
However, NZ Council for Civil Liberties chairman Thomas Beagle said from a civil liberties perspective, it was "more snooping" for what appeared to be a small pay-off in terms of border protection.
Casting net wider
Customs is looking at adding to the list of goods it tracks as controlled deliveries beyond weapons and drugs. New items could include:
• Objectionable publications, such as DVDs or books
• ATM and credit card skimming devices
• Counterfeit money