North Korean leader Kim Jong Un said in a statement that the new law would make the country's nuclear status "irreversible" and would stop any future potential denuclearisation.
North Korea has passed a law that allows the use of nuclear weapons in a pre-emptive strike to protect the country.
The new law comes as Kim Jong Un accused the United States of pushing an agenda designed to weaken the defences of the country and eventually collapse his government.
Kim said that the law would ensure that North Korea's nuclear status was "irreversible" and bar any future denuclearisation talks, state media reported on Friday.
Experts claim that North Korea is preparing to resume nuclear testing for the first time since 2017, after historic summits with then-US President Donald Trump and other world leaders in 2018 failed to convince Kim to scrap his nuclear weapons development program.
State news agency KCNA reported that the Supreme People's Assembly passed the law on Thursday.
Kim gave a speech to parliament, saying: "The utmost significance of legislating nuclear weapons policy is to draw an irretrievable line so that there can be no bargaining over our nuclear weapons."
In the country's constitution, North Korea had already declared itself a nuclear weapons state, however, this new law goes beyond that, outlining when nuclear weapons are allowed to be used, including responding to an attack or stopping an invasion.
The law also permits a pre-emptive nuclear strike if North Korea detects a threat to any "strategic targets", or if the country is at threat of an imminent attack by weapons of mass destruction.
Kim Jong Un has said that the United States and their allies maintain "hostile policies" such as sanctions and military drills that undermine their messages of peace.
Kim said: "As long as nuclear weapons remain on earth and imperialism remains and manoeuvres of the United States and its followers against our republic are not terminated, our work to strengthen nuclear force will not cease."