I don't think Anarchist means being opposed to EVERYTHING the government does, but being opposed to the government itself as an institution. If the government allocates tax money and/or its policing power to something that does more good than harm (not saying this is really possible to calculate), then I have no problems with it. In the case of some environmental regulations, the government is certainly using it's own power to clamp down on an organization it usually protects. For example, it would be stupid in my opinion for an anarchist to oppose the government stopping some company from poisoning children.
However, that being said, is the government in the long run actually capable of protecting "it's people", or will it just make things more difficult for people in the long run, and encourage more consumption by claiming that markets and a clean environment are actually compatible? The only difference I see between today's modern "corporatist" capitalism and the capitalism of the past is that companies have gotten so goddamn good at whitewashing and covering things up.
To me, trying to petition for environmental regulations is just a huge waste of time, and we would be better off resorting to other methods...