Thats the thing, though. "Umodified" Internet would not be able to be throttled down. Every ISP now is doing traffic shaping when they are setting you fixed arbitrary and often tiered data rates on your lines. That is never the limit of what the physical hardware is capable of, its a number set on their outbound WAN routing servers to accept or deny going in or out to your IP address.

But if you did have a legal definition of Internet requiring unmodified traffic, ISPs selling Internet service would have to, by definition, provide unlimited bandwidth insofar as their physical links are capable of. Which might actually be nice - we already know coax is fully capable of pretty incredible speeds, and being able to push data as fast as you can onto that link would be invaluable.

Of course, that also means the ISP has no requirement to ever upgrade their routing hardware - they would just have cheap stuff running 100% full load 24/7. But then its a consumer choice what ISP you use and whose hardware is best for the money - more expensive ISPs would be offering better routing hardware that can handle higher traffic, and cheaper ones would do the opposite. Well, that would work, if you lived in a sane country where infrastructure like coaxial lines or twisted pair or fiber to the home were public services rather than privately owned and monopoly controlled.