Because every single nation would have to sign on to it allowing said agency to ignore sovereignty of each nation to come in and do their policing.

You'd also need to have every country not actively involved in these types of schemes yet we know some governments are directly benefiting from the scams/theft their citizens are perpetrating.

You'd also need to have every country think the things you want to police against are wrong. Again, we know that's just not true.

How did we (USA) so it with copyright law?