Wong, who was secretary for justice between 2005 and 2012, was speaking at a seminar on the Basic Law at the University of Hong Kong.

“We must understand and accept that from the constitutional and legal perspective, the National People’s Congress Standing Committee undoubtedly has the power to interpret every single clause of the Basic Law,” he said.

“But at the same time, there is no doubt that such power must be exercised with extreme restraint and only when it is unavoidable.”

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The standing committee’s interpretation detailed requirements for a valid oath in Legco. It said lawmakers-elect must read out the complete oath precisely and solemnly. If they deliberately changed the wording or appeared to be insincere, they must be ruled to have declined to take the oath, it stipulated.

The local courts eventually sided with the government and removed Leung and Yau. Subsequently, four other pan-democratic lawmakers were also kicked from their Legco seats because of their oaths.

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Referring to the intervention by the standing committee, Wong said: “I find it a pity. It should have been avoidable.”

He noted that the three different levels of local courts all said they would have disqualified Leung and Yau even if Beijing had not made the move.

Since Hong Kong was handed from British to Chinese rule in 1997, the standing committee has interpreted the Basic Law five times: in 1999, 2004, 2005, 2011 and 2016. The first three times were over a right of abode issue, political development and the term of the chief executive, while the fourth was about “state immunity”.

Wong said last November’s interpretation was different from previous ones, adding that the reasons for the first four were “non-political”.

According to Article 158 of the city’s mini-constitution, the power to interpret the Basic Law is vested in the NPCSC.