I'd say most issues fall back on the end user. My issue with compliant units is, some 'Joe College' at the EPA initiated all of this and probably never even ran one...
It's easy to compel emissions mandates when the 'mandater' is an armchair person.
Joe College had nothing to do with it. Joe, the Engineer who is very familiar with what a Diesel Engine is. He is the person that designed the re-gen system and had a lot to do with it though.