Tonga's Democratic Party is hoping the King will not give assent to legislation that dramatically reduces the penalties for offences under the Arms and Ammunition Act.
The amendments would cut the maximum sentence for illegal gun and ammunition possession to one year or less and drastically reduce the fines that could be levelled.
The private members bill was introduced by a party member, Sangster Saulala, but the other Democratic Party members opposed it.
However the legislation passed with the backing of the nobles - two of whom are facing charges under the old legislation.
The deputy leader of the Democratic Party, Dr Sitveni Halapua, says it's now up to King George Tupou the 5th.
"If the King puts his signature to it it will become law of the land. If not, if the King vetoes it, that means that that piece of legislation will not become law. That's our last hope now to see how the King is going to exercise his veto right."
The two nobles facing charges, Lord Tu'iha'ateiho and Lord Tu'ilakepa, would lose their titles and seats in Parliament if convicted under the current legislation.