Your strawman is that there was some regulation, so that proves that regulation doesn't work. Perhaps BP should argue that they had some mechanical safeguards at the well head that were supposed to keep this leak from happening and those safeguards didn't stop this disaster, so obviously the lesson here is that safeguards are not the answer.
If you're arguing that government is inherently so corrupt and incompetent that it's impossible for it ever to regulate effectively and so we should stop trying, that's a slightly more valid argument, but I'm going to have to disagree with you. It's not an easy problem, but that doesn't mean we shouldn't try.
We're talking about giant, ridiculously wealthy multinational corporations. The government is the only hope that people have of making any sort of stand against them. The fact that it's imperfect and requires serious work to function properly is a shame, but I fail to see how doing nothing would be any better.