Activists arrested for oil graffiti in gulf, but where are the BP arrests?

Let's get this straight: when Greenpeace activists board an oil-drilling vessel and write "Arctic Next?" in leaked Gulf Coast oil on the bridge, they're immediately arrested, yet no arrests have been made for BP/Deep Horizon executives who, through negligence and lack of planning for worst-case scenarios, have dumped six million gallons of oil (and counting) into the Gulf of Mexico?

The White House could prosecute, but the language is so wishy-washy it seems doubtful: A report by The Independent says the administration will file a formal inquiry which "could lead to possible prosecutions."