The national parliament passed a bill to amend 2011 Transitional Constitution to allow President Salva Kiir to proceed with creation of states and appointment of governors and lawmakers.
The president in early October created 28 states out of the 10 enshrined in the constitution, Radio Bakhita reports.
Parliamentary Speaker, Manasseh Magok, announces unanimous approval of the changes in the constitution by the Augus House as supporters clap hands.
But, Minority Leader in parliament, Onyoti Adigo Nyikwec protested, saying the amendment is not lawful.
He and six other MPs walked out of parliament.
MP Adigo says the number of parliamentarians required to amend the constitution has not reached 2/3 as stated in the law.
37 Members of Parliament from the Equatoria region earlier boycotted the session.
They say the amendment of the constitution undermines peace agreement that government commits to implement.
For now, the approved changes in the constitution require President Kiir to sign to become active law.