I’m not sure what “go after” means in this context. OPEC is a group of countries, so it’s a diplomatic issue. And the west does apply pressure on them to behave

I’m not sure what “go after” means in this context. OPEC is a group of countries, so it’s a diplomatic issue. And the west does apply pressure on them to behave in certain ways. But it’s diplomacy or warfare, not a legal issue.