Japan's so-called "self-defence" constitution, introduced following it's defeat in World War Two, bans the use of military force to wage war against other countries.
Current Japanese law also prohibits the introduction, development, or possession of nuclear weapons.
Shinzo Abe, the Japanese prime minister, has said he would stand behind the government’s non-nuclear policy, despite viewing North Korea as a leading source of instability in the region.
Japan is the only country to have been hit by nuclear weapons in war time.
The cities of Hiroshima and Nagasaki where targeted in August 1945 in US raids that supporters say helped push Japan to surrender and bring a speedy end to World War Two.