De facto law minister Liew Vui Keong said in a parliamentary written reply that this was because every citizen had the right under the Federal Constitution to form associations.
Liew cited a Federal Court case involving the Kelantan state assembly and Nordin Salleh in 1992. PAS had its own anti-hopping rule then, and when PAS assemblyman Nordin switched to Umno, the case went to court. The court ruled that such a rule was void as it violated freedom of association under Article 10 of the constitution.
Liew was responding to Lim Lip Eng (PH-Kepong) who asked the prime minister to state if there were any proposals to introduce anti-party hopping laws to stop MPs from quitting the party they had contested under during the general election.
PAS had urged the Pakatan Harapan government to draft an anti-party hopping law following recent cases of elected representatives switching parties at will.
A total of five MPs have quit Umno since the general election: Jeli MP Mustapa Mohamed, Kimanis MP Anifah Aman, Masjid Tanah MP Mas Ermieyati Samsudin, Bukit Gantang MP Syed Abu Hussin Hafiz Syed Abdul Fasal, and Bagan Serai MP Noor Azmi Ghazali.