Attached below is the Joint Policy Declaration by the United Nations countries Participating in the Military Action in Korea Affirming to Carry out the Terms of the Armistice signed by Australia's Percy Spender and registered with UN as part of the Armistice Agreement (the entire Armistice Agreement can be found online at the Gerald R. Ford Presidential Library and Museum).
The Joint Policy Declaration states:
"We affirm, in the interests of world peace, that if there is a renewal of the armed attack, challenging again the principles of the United Nations, we should again be united and prompt to resist".
Is this an obligation? Australia's Official Korean War Historian believed so, as he noted in his Korean War Memorial Oration in 2003:
"Today South Korea is essentially self sufficient in defence terms, although its UN Command allies, including Australia, remain obliged by their signatures on the Joint Policy Statement of 27 July 1953 to come to its aid if hostilities break out again".
Politicians seem to pick and choose dependent on the moment and their position. Clearly, there is no cut and dry answer - but there is also clearly a justification for Australian participation to come to the defence of South Korea if attacked.
In any case, wouldn't it be better if Australian Prime Minister Malcolm Turnbull used a multilateral commitment to deter aggression to justify an Australian role rather than being "joined at the hip" to the current President of the United States?