The relevant facts are these: 1) Very powerful political interests in Washington insist upon the scrupulous enforcement of environmental laws, and if that diminishes the interests of private property owners, so much the better, in their view. 2) Very powerful political interests in Washington do not wish to see the scrupulous enforcement of immigration laws, and if that undercuts the bottom end of the labor market or boosts Democrats’ long-term chances in Texas, so much the better, in their view.
I think this is wrong, but wrong in a way that reinforces Williamson’s larger point about the arbitrariness of contemporary governmental power. My understanding is that environmentalists and the EPA have repeatedly gone to court to keep environmental laws from being applied with the strictness that the letter of the law would demand, because strict enforcement would politically undermine the agency, the environmental movement, and the environmental laws. The Supreme Court, for example, ruled in 2007 that carbon dioxide emissions are a pollutant for the purposes of the Clean Air Act. Applying the terms of the act to carbon emissions would, however, produce absurdly strict results, so the Obama-administration EPA wants to be able to rewrite the statute. The whole thing is, I believe, still tied up in court. (I hope Jonathan Adler will weigh in here if I have this stuff wrong. Michael Greve described the issues a few months ago.)
In environmental law as elsewhere, enforcement seems to be selective rather than scrupulous.