Nerd Analysis: 2 Law Professors on Wisconsin and Public Sector Unions

I had previously linked to a prof's take on the Wisconsin showdown here.  Two other professors (both in law) weigh in here and here.  The second one is short enough to quote:

In response to a commentator who chastises me for not speaking to the merits of public sector unions, I shall do so. Public sector unions ought not exist. Here’s why. 

In the private sector a union bargains for a greater share of the entity’s revenue and profits. What it can provide in return is greater productivity, accomplished perhaps by work force stability, higher morale, and the belief that the common fate of employer and employee will be enhanced by productivity gains. If this happy event ensues, at the next round of collective bargaining, union workers can and should receive their fair share of the resulting gains. 

In the public sector, by contrast, a union is not bargaining for a greater share of the revenue produced by economic activity; it is bargaining for a greater share of revenue that is obtained by force of law – taxation – or, if not a greater share, at least for a constant share of those revenues extracted from the citizens. What a public sector union can and does provide in return is political support for the faction that chooses to increase taxes or the union’s share of existing taxes. If public sector unions deliver on their support, they will be rewarded by ever more generous payments. There is no market that acts as an external monitor of worker compensation; there is only a steady repetition of a corrosive bargain – tax the public ever more in order to maintain political power. That is inimical to responsible government.