While reading out the verdict, Chief Justice Nisar said that a person who is disqualified under Articles 62 and 63 of the Constitution is not eligible to sign on any document needed to nominate someone to the National Assembly or Senate.
The decision was made by SC after the apex court found former Prime Minister Nawaz Sharif guilty in the Panama Papers case.
Mr Sharif and his supporters have repeatedly denied allegations of corruption, suggesting the three-time prime minister is the victim of a conspiracy driven by Pakistan's powerful military establishment.
A batch of petitions challenged the act in the Supreme Court.
Maryam Aurangzeb, information minister, said the court ruling was not unexpected.
It said that all decisions taken by Sharif in his capacity as party chief stand null and void.
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Terming the todayâ€™s SC judgement in Election Act 2017 against the basic principles of justice, PML-N spokesman said one could not find any such example of this kind of ruling in democratic history.
The judgement into Elections Act 2017 followed 17 petitions - filled in the Supreme Court by Pakistan Tehreek-e-Insaf (PTI), Pakistan People's Party (PPP) Awami Muslim League (AML) and others - against the controversial act which had authorized Nawaz Sharif to take over PML-N again despite being declared "dishonest" by the apex court.
He also noted that Sharif had attended all of the court hearings and if fleeing would had been an issue, the court would had ordered the travel ban.
The decision, while expected, has created uncertainty about Pakistan's political stability, said political analyst Hasan Askari. The Chief Justice added, "No parliamentarian was called thief".
"It is yet to be seen how the verdict will affect PML-N's politics, while the ECP will have to decide the validity of the by-elections that have taken place since Sharif's disqualification", Hussain explained.
They also content that the law is against the spirit of the Constitution.