It appears that the ban is part of the Marine Mammal Protection Act of 1972. The EU has now also passed a ban on the import of seal skins as well as other countries. I haven't found evidence that posession of seal skin is illegal however, if import has been banned for 37 years, I would assume (read I'm not a lawer so I don't really know) that ownership of seal byprodcts manufactured, or imported, since that time are also illegal. That's why I purchased a muskrat skin sporran instead.