No-one has been executed in the Kingdom since 1982, and a de facto moratorium has been maintained since then.
But it still remains an option for convictions of murder and treason.
Last month, Adrian Morrison, co-hosted an event to commemorate World Day Against the Death Penalty.
He identified the death penalty as "one of the few points of genuine difference between Australia and Tonga."
Mr Morrison said Australia was not only against the death penalty, but was actively working to convince others, including Tonga, to abolish it.