Will Wilkinson explains:
The power to tax and spend is necessary for the performance of the democratic state's legitimate functions, but it is also a ready tool of exploitation and distributive injustice. An ideally legitimate state does nothing people can do better on voluntary terms, and it takes no more from people in taxes than is necessary to finance necessary public goods. But this is a moral target we never hit because the strategic logic of redistributive democracy reliably errs in the direction of expansion of services, deficit spending, and the abuse of taxpayers and other not-very-organised constituencies at the hands of highly-organised special interests. If we are concerned to minimise exploitationif we care about the extent to which state violence is public-spirited and not merely criminalwe must go out of our way to acknowledge and guard against the abuses of fiscal democracy.
It is in the context of these concerns that we must consider the function of public-sector unions. If they do anything at all, it is to protect their members' claims on future government revenue from democratic discretionto limit the power of the elected representatives of the democratic public to set the terms on which union-members will receive transfers from taxpayers. That these transfers come to workers in the form of compensation for services rendered the government seems to confuse a lot people. This is, I think, why people on both sides of the debate are distracted by the question of whether government workers are or are not "overpaid". To my mind, the real question is whether government workers should be granted special legal powers that (a) are unavailable to other groups whose welfare also turns on transfers from the treasury, or on the size of compulsory transfers from their bank accounts to the treasury, and (b) limit democratic sovereignty over the distribution of the burdens and benefits of the system of public finance.
He concludes that his "principled objection to public-sector unions is that their powers limit democratic sovereignty over taxation and public spending in a way that advantages some citizens at the expence of othersin a way that makes fiscal exploitation more, not less likely. Should they have grievances about their cut of the public budget, non-unionised government employees have recourse to the exact same democratic institutions as do other groups of citizens, which is as it should be."