Just using a 23-channel radio, even if it isn't modified stopped being legal around 1981 or so IIRC.
I think I remember that being discussed before around here and that it is not factual. It would of course be illegal to manufacture and market them as new but there isn't any reason that an older 23 channel rig cannot still be used and of course a great many of them are sold privately as used and maybe even a few new old stock at times.
They were type accepted at the time they were manufactured/sold and that should be grandfathered if a problem at all. Chances are that spectral purity concerns were the same before and after the change.
The older 23 channel radios are just a bit of a lesser radio in features than a new one but still can be usable and kept within specs for what it is. They had no features that are now illegal to use.
I don't think they could make the zillions of them already out there at the time illegal to use expecting everyone to go out and buy a new one when the older model works just fine for their purposes. Especially if you had just bought it a short while ago. Just not practical and a great many may have never even known about it.
Would the same apply to all the different 5 watt walkie talkies and older rigs that only have a few, maybe 3 or 5, crystal controlled channels too?
They really can't just say "Okay, it's 40 channels or NOTHING now! And there was/is no reason to.
The manufacturers and CB shops would like that though! Big bucks!!
One of my favorite historical figures would say "It's not what you do, it's what you get caught doing".
Pretty weak from a moral standpoint. I used to be a county corrections officer. The place was full (literally) of people that thought that way. In some smaller ways it doesn't matter as much I suppose but it does get carried way to far. Do the right thing.