A senior Taiwanese presidential adviser argues Beijing's legal case for "One China" over Taiwan does not hold up, a boost for Taipei's push for international standing.

• Presidential Office adviser Yao Chia-wen said the 1951 San Francisco Peace Treaty had Japan give up Taiwan without naming who receives it, leaving Taiwan's status legally open.
• China leans on the 1943 Cairo Declaration, but that was a statement of intent, not a binding treaty like the San Francisco one.
• Neither Chinese government was invited to sign in 1951 because the world could not agree which one represented China, so the question was left hanging.
• UN Resolution 2758 only moved China's seat from Chiang Kai-shek's government to Beijing and never said Taiwan belongs to China.
• Taiwan's own diplomats are said to barely know this history, which weakens how the country argues its case abroad.

Outlook: Expect Taipei to keep pressing the "undetermined status" argument and calls to teach it in schools as China escalates its claim.