Leadership Spill Rules from the Constitutional Perspective

Recently both major political parties have adopted rules increasing the security of tenure of their federal parliamentary leaders. Both parties now require a specially high majority of their parliamentary members to bring about a vacancy in the leadership. For example, a Prime Minister who is federal Australian Labor Party leader cannot be removed from the latter post unless 75% of the members of the parliamentary party support such action. This article documents and analyses those rules and then asks three questions. First, can the rules be repealed by ordinary motions in the two party rooms without any special majority, restoring the previous position under which a bare majority was sufficient to unseat the leader? Second, are the new rules legally enforceable? And third, what should be Crown and the courts do if there is a dispute about who the rightful parliamentary leader and thus Prime Minister is?