Hailed as East Timor's founding father, Xanana Gusmao was greeted by supporters in The Hague as he arrived to present the country's case at the permanent court of arbitration.
Inside, the country's former leader issued a plea for a better deal with Australia.
"The basic fairness and common sense, let alone international law, dictates that the maritime boundary between two opposite countries should stand half-way between them."
He was joined by Elizabeth Exposto, head of the country's maritime boundary office.
She spoke of just how important the billions of dollars in oil and gas royalty revenue would be to the fledgling nation's future.
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"With the majority of our population under the age of 25, our hope for nation-building lies in the future and it is up to the representatives of Timor L'Este to secure a better future for our young generation and their children."
Under the current treaty, royalties from lucrative oil and gas fields are split 50-50.
But if the maritime boundary was to be drawn half-way between the two countries, those fields would be entirely in Timorese waters.
Xanana Gusmao says it's simply what his country is entitled to.
"We have not come to the Hague to ask for favours or special treatment - we have come to seek our rights under international law."
But back in Australia, Foreign Minister Julie Bishop has been taking a hard line.
She says the royalty revenue was agreed under a mutually beneficial treaty ten years ago and under that deal, both sides agreed to a 50-year morotorium on negotiating definitive maritime boundaries.
East Timor is trying to have that agreement annulled because its ministers were spied on in the lead-up to the signing.
Foreign Affairs Department lawyer Gary Quinlan has urged the international court to reject that bid.
"Timor-Leste talked about alleged Australian espionage. Timor-Leste has brought a seperate arbitration claiming that CMATS is invalid on these grounds. Australia does not accept Timor-Leste's claims and is defending the validity of the CMATS treaty in those proceedings. Australia's position is the Commission should not disregard our treaties simply because because one party has changed its mind."
And besides, Australia maintains, the court itself doesn't even have the power to hear the dispute.
