Thanks for the reply Walt Sherrill,
I am not sure of the details. I understand that the law is currently being appealed and is (I think) on hold pending the court action. From what she has told me:
you cannot buy nor sell magazines > 10 round
you cannot possess them
you cannot transport them
you cannot ship them
you must destroy, convert to less than 10 round or turn in to (police or someone not clearly specified)
This makes it difficult to deal with them as you are not allowed to get them out of the state, to a gunsmith for conversion nor to whomever you are supposed to turn them in to. I guess you are supposed to hire a gunsmith to come to where the magazines are to "convert" them although what constitutes and approved "conversion" is of course not specified in the law. Etc.
A couple of years ago I de-Glocked my collection. A local dealer listed a couple on gunbroker for me and handled the transfers. A G21 went to a buyer in Connecticut I think it was. He was more interested in the fact that it had several non-drop free mags than the pistol itself. These were made during certain years and were clearly "pre-ban" from the state's point of view. I am left with several brand new G21 drop free mags for which I have no use.
Let me not get on my soapbox

Ken