Hardcore libertarians never get around the issue of imperfect information and of transaction costs.
Rather than have environmental regulations that we all have to abide by and that a small fraction of our tax dollars go to pay to enforce, they'd rather we all sue each other every time someone pollutes. Never mind the time and money involved, and the fact that the polluters (major corporations) would automatically have more resources to prevent this than Joe Somebody who makes $40K a year and can't pay a retainer and $500/hr attorney bills.
I've heard a couple libertarians argue for environmental regulation for the same reasons that they criticize anarcho-capitalism. That is, the poor cannot do anything about someone harming them or their property, so the state must step in.
