Where to now for Donald Trump? North to Asia or across the Pacific? I won’t pretend to know the answers to these perennial questions of Australian foreign policy, but perhaps I might colour the legal context. What seems clear is that President Trump is going to require some extraordinary zeal if he hopes to crack the backbone of the Australia-US alliance.

It might be tempting to view the volatility of the USA’s freshly minted President as a threat, even an existential one, to the historic alliance between our two countries. However, the alliance has proven particularly durable, both in itself and in the willingness of its parties to preserve it.

Notably, the alliance is what remains from the treaty formerly known as ANZUS. New Zealand is no longer a party to ANZUS, and the precipitating factor for the nation leaving this treaty was an incident involving the USS Buchanan. A bit of backstory: New Zealand denies port to any vessel which is nuclear powered or carries nuclear material. During an incident in 1985, however, the Reagan administration insisted upon the Buchanan being permitted to dock; New Zealand, of course, refused. This set off a diplomatic incident which led to the US suspending their treaty obligations toward New Zealand.

Under international law, there is a general right of ships to dock at foreign ports which dates back to a 1923 convention, and confirmed in a 1958 Saudi-Arabian arbitration. However, the Law of the Sea Convention (LOSC) provided that nuclear-equipped vessels could be subject to a particular regulatory regime. So, both of the states had could claim they were in the right, but given the context of ANZUS surely New Zealand’s refusal was both surprising and inappropriate.

Notably, while New Zealand had not ratified the LOSC, it had signed it. This indicates that they were willing to be bound, but the Article in question did not officially bind them. That legal status, combined with overwhelming support by the public for the anti-nuclear rule – both historically and current – gave New Zealand enough of a basis to deny the request.

The Reagan administration’s desire to bullishly advance American interests, something which may sound familiar, was a factor in this hard-line approach. However, realistically, downgrading from an ally to a friend did not break the relationships between the US and New Zealand, with many joint military activities to follow in the coming decades.

Reagan does provide an interesting allegory. Another feature of that administration’s conduct in this area was the hugely disruptive effect they had on the negotiation process of the LOSC. The negotiating process ran from 1973 to 82 and looked largely on track to a productive consensus. That was until Reagan got elected and tanked a lot of the negotiations because he was concerned that developed states wouldn’t get enough out of deep sea mining provisions. This tumult meant that the LOSC didn’t enter into force until 1994.

It seems like Trump is more likely to agitate where it is customarily possible to do so than overturn history and agreements. This may be somewhat evident through the following three case studies in Trump: The Trans-Pacific Partnership, the South China Sea, and the Australia-America refugee agreement.

Trump withdrew from the TPP during negotiations. He most certainly upended some expectations, but at no point was the US bound to fulfil any obligations which might arise under the TPP.
Trump continues to act as international law police in the South China Sea, and has been conducting military exercises in the sea since his inauguration. The disputed region was recently subject to an arbitration award calling into question the extent of Chinese sovereignty. The US, however, also has a history of sailing its warships into disputed waters to make clear their protest to the claim; it seems Trump is merely continuing the highly vigilant policy of the US to test and protest excessive territorial claims of this kind.

Then, regarding the recent refugee deal, Trump insisted that it was ‘dumb’ – but followed through anyway. This suggests that Trump, as volatile as he is, will oddly walk the walk even if he doesn’t talk the talk. Even if he’s foggy on the protocol, it seems Trump is at least somewhat sensitive to international custom.

Customary international law is formed from a combination of state practice and the opinion that law or necessity compel such practice. Trump may not have desired a deal to accept Australia’s refugees, and it very much conflicted with his domestic attitude. However, he recognised that a promise had been made and that it was sufficiently necessary that he comply with the terms. Then, of course, there is the wild card – where Trump’s sheer unpredictability gives rise to some degree of diplomatic calamity, on some scale bilateral to global. Maybe this will come to pass, but for now the evidence would suggest that though Trump’s tendency may be to bloviate, he will then fall in line with what international custom states should happen.

The ‘Muslim ban’ is a key case to illustrate this inclination. The ban itself may seem ridiculous, and a departure from custom, but it also shielded Trump’s business connections from its wrath. While there is no doubt madness, perhaps that is the method: Trump knows to be kind to his interests. It looks like for the time being the US’s non-allies are to be further maligned, and though his allies may be tested, they will likely endure.