I have previously discussed a political system where political parties in proportionally representative system are allowed to set up their own rules for deciding their vote (link). This is unlike traditional closed or open list systems where the decision rule is fixed by the political system. I have been wondering about the risks posed by letting political parties define their own rules for determining how to vote, as I have suggested before. The major risk that I see is to the various separations of power. The risk is that parties could figure out ways to have voting abilities in multiple political institutions which are not independent on each other. If parties in different government institutions had agreements with each other to collude in making decisions, the separation of powers would begin to be worn away.
Would it do to simply add a constitutional clause that parties are not allowed to legally associate with parties in different government institutions? I am not sure if this would just be a ‘parchment barrier’ (though some parchment barriers seem to have been remarkably effective) or a real, enforceable institutional rule. My concern is with enforcement; enforcement would ultimately have to come from the courts, but I am not sure if a Supreme Court would have the appropriate incentives to enforce such a rule; after all, the courts are appointed jointly by legislative and executive bodies, which are composed of political parties. Perhaps this is something that separation of powers actually combats because of ‘ambition counteracting ambition,’ so that as long as the parties in the executive and legislative branches are strongly separated, they will appoint judges who will maintain that separation.