There has been talk here and there about the legality of 'repurposing' vintage and antique seal skin products into sporrans, since seal skin itself cannot be imported, either directly or indirectly. As a sporran maker myself, I felt I had to read up on this closely. From what I can see in the text of the actual act, as passed, and as amended, it looks like this is fully lawful:

Sec. 102, subsection e:

This Act shall not apply with respect to any marine mammal taken before the effective date of this Act [December 21, 1972], or to any marine mammal product consisting of, or composed in whole or in part of, any marine mammal
taken before such date.

Seems to sum it up well enough. There is also an exemption listed earlier on in the Act that states you can bring your seal skin sporran back into the country if you leave with it (6Ai): "was legally possessed and exported by any citizen of the United States in conjunction with travel outside the United States, provided that the product is imported into the United States by the same person upon the termination of travel."

Of course, the fun part is the proof...