The Impossibility of Ranking Rights

In Hudson County Water Co. v. McCarter, a 1908 decision of the US Supreme Court, the celebrated Oliver Wendell Holmes stated that all rights "tend to declare themselves absolute", yet all in fact are "limited by the neighborhood of principles of policy" and the boundary at which the conflicting interests balance "cannot be determined by any general formula in advance". The only reasonable thing to do is fix some "points in the line" by decisions that "this or that concrete case falls on the nearer or farther side". This will help in deciding further cases.
In decision 85/2013, the Italian Constitutional Court stated that "no right is tyrant". It meant that all rights, including constitutional ones, must be balanced against competing rights and principles. The case concerned some measures about the Ilva plant in Taranto and the need to strike a balance between right to health, right to work, right to a clean environment, and the economic value of production. The Court made it clear that no right can be so strong as to always impose itself on the others.
No existing constitution establishes a definite hierarchy of rights and principles. There is no "general formula in advance", as Holmes put it. In this respect, the Federal Constitutional Court of Germany has elaborated a pattern of "proportionality analysis" that is supposed to assess the balance between competing rights, and Robert Alexy, a well-known legal theorist and philosopher, has refined this pattern of analysis and enhanced an international discussion about it.

But the discussion has polarized into two competing theses. In one view, balancing is both irrational and subjective. When courts "weigh" conflicting constitutional rights, they actually make choices based upon considerations that cannot be rationally justified. One of the reasons for this is the supposed incommensurability of principles and values. In the other view, balancing is a rational argumentative framework grounded in the very structure of constitutional rights and principles. And according to an economic understanding of it, it can be taken as a form of cost-benefit analysis.
The supporters of the two views tend to polarize toward the extremes, and neither of these competing theses is true. In our understanding, it is possible to analyze the argumentative structure of balancing decisions and show that they are composed of multiple steps. If we make them explicit, we can see under what conditions they can be justified in a given constitutional legal system. So, balancing is neither rational nor irrational per se. The rationality conditions of balancing depend on the justification of its multiple steps.
Consider the obligation to put health warnings on tobacco products. Tobacco producers in Germany claimed that it interfered with freedom to pursue one's profession. The Court considered it as a relatively "light" interference with that right. In particular, the Court noted that it was lighter than other possible legal measures: a total ban on tobacco products would count as a "serious" interference, and restrictions imposed on tobacco sellers as a "moderate" one. The same scale was applicable to the competing reasons. The health risks resulting from smoking are high, so imposing health warnings promotes the protection of health and high expected benefits, stated the Court.

If we analyze the argumentative steps of the decision, we can understand whether they are justified. It is true that the obligation interferes with freedom of profession. And according to scientific evidence it is true that risks associated with smoking are high. Is it also true that health warnings are effective in discouraging people from smoking? To answer this, one would need an accurate account of the actual and expected consequences of the warning. If one just speculates about it, one cannot dismiss the relevant argumentative commitment. Contrary to what has been claimed in the literature, predicting the consequences of the decision is the real crux of balancing.
To conclude, the balancing metaphor risks being confusing if it suggests that rights and principles can be exactly measured on a scale. They cannot. But we can construct and assess informed and reasonable arguments about them.