So, anyone who can successfully define what they're doing as "not prioritizing" can entirely sidestep any regulation you have in mind.
Putting a server in the ISP's datacenter is a common approach. Traffic to those servers doesn't have to go over any external peering links.
> ISPs should not and do not apply QoS in their core
Many do. As one simple example, look at the ISPs that accelerate the first N bytes of connections, to prioritize interactive requests over bulk transfers/downloads. Other ISPs apply more sophisticated approaches.
> It's pretty obvious how you draw that bright line. Don't prioritize and don't congest interfaces.
> forbid prioritizing and saturation of network interconnects
So, receive and deliver all traffic, regardless of available capacity or financial constraints? Provision every part of the network so it can handle all the traffic passing over any other part, because they're not allowed to limit bandwidth in any way at any point?
A saturated interconnect might mean "we're trying to screw Netflix", or it might mean "we can't afford it right now" (either because they're a small ISP and don't have the money, or because they're spending it on something their customers want more).