"No one is saying drugs are good for you. However, the system we have in place is simply not working," Isaiah said.
"The 'War on Drugs' is cruel and racist. It's time to move to a more humane and compassionate system, where drug users are given the treatment they need to recover, and police can focus on actual crime.
"I'm looking forward to working with other sectors in the Labour Party - and other youth wings - to advance this issue. Now's the time for change."
Health Minister Andrew Little has repeatedly said that decriminalising drug use would fly in the face of the last year's referendum result, where the vote narrowly went against legalising cannabis for recreational use.
In response to the open letter, Little and Ardern poured cold water on major drug law reform, saying they wanted to see if the 2019 law changes are having the intended impact.
That law change has seen prosecutions for drug use/possession - where that is the most serious offence - fall compared to the year before the law change.
But about a quarter of those facing charges are still being prosecuted for drug use-possession, while only about one in 100 users that police come across engage with a health referral.
It's the latest youth wing pushing for more liberal drug law reform policies than its party.
Last year, young NZ First and Young National supported drug-checking at festivals. NZ First then softened its stance and called for more research.
Before this summer's festival season began, the Government changed the law temporarily to give director-general of health Dr Ashley Bloomfield the power to make drug-checking services explicitly legal, a change which the Government now wants to make permanent.
In contrast to Act party policy, Young Act wants to legalise illicit substances that are considered to be low risk, including cannabis, psilocybin (magic mushrooms), LSD, mescaline and MDMA.
