Speaking on radio station DWIZ in the Philippines, Pacquiao said: "This is not about me or what I want but this is in the Bible and also in our Constitution, so there is no problem."
The senator has already filed three separate bills to revive the death penalty in the country.
He wants to see it imposed when the crimes committed are drug trafficking, rape with murder, kidnap for ransom and robbery with murder.
Last week Pope Francis changed the Church's teaching on the death penalty by saying it can never be approved because it attacks the inherent dignity of all people.
The Vatican said that the pontiff changed the catechism of the Catholic Church - the compilation of official Catholic teaching.
Previously, the catechism said the Church did not exclude recourse to capital punishment "if this is the only possible way of effectively defending human lives against the unjust aggressor".
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