here's the scoop as I know it:
EAA (the american importer of the Saiga) will not import them due to the fact that the magazine in itself does not meet sporting criteria as set forth by the ATF.
If the products sold by EAA are under scrutiny to maintain the "sporting criteria", it could possibly slow or halt any further importation of the firearms, if it's found they are questionable for sporting purpose. That would mean a reduction in sales for EAA..
Then there is also a question about "if" the magazines become prevalant, the ATF could possibly classify the 12 guage (Saiga) as a "Destructive Device". Similar to what happened to the Street Sweeper.......I don't see the magazines readily available.....ever.
They are however available in Europe, I am still unclear about the legalities of that. The ATF told me that I would need a form 6 part 1 to do so, and then there is rumor that if it's under $100, it's OK to personally import a very small quanity (say personal use only)