[fireman15]

The same thing could be done here, except with ‘emission standards’. Can’t pass the standard, can’t register the car. Easy Peasy.

I don't know where you live... they already do that here in the urban areas of the great Pacific Northwest.

[hanamizu]

No smog testing here in SE Missouri. The difference, though, between what you deal with now and what could happen, is they will make the smog tests impossible to pass—with no grandfathered provision for really old vehicles.

[5th MEB]

Do like the WETBACKS, just steal a current registration tag from another car!