In practice, this does not prevent parallel imports: indeed the grey market in the US was valued by Deloitte at USD 63 billion in 2009. Importers rely on section 109(a) of the US Copyright Act which says that anyone who buys a work which is "lawfully made under this title" (meaning under the Copyright Act), may re-sell that work without the permission of the copyright holder. This is the first sale doctrine, which is similar to the principle of exhaustion in Europe, both of which aim to allow a second hand market for goods.
In this case Supap Kirtsaeng, originally from Thailand, realised that he could import textbooks from Thailand and sell them in the US, on eBay, at a profit. John Wiley & Sons a textbook publisher noticed that Kirtsaeng was re-selling some of its textbooks. These were editions intended for distribution outside the US. They were of slightly lower quality and were of course sold at a much lower price, enabling Kirtsaeng to make a profit of USD 37,000.
Wiley sued Kirtsaeng for copyright infringement, and the judge at first instance barred Kirtsaeng from relying on the first sale doctrine as the books were manufactured outside the US. The first instance judge found in Wiley's favour and awarded damages of USD 600,000. This was upheld on appeal: the 2nd US Circuit Court of Appeals held that the first sale doctrine was inapplicable because the wording "lawfully made under this title" at section 109(a) referred only to copies manufactured in the US. The case now proceeds to the Supreme Court.
This time around Kirtsaeng's legal team is arguing that if the appeal is dismissed by the Supreme Court any businesses which rely on resales (such as eBay), as well as second hand cars (containing copyright protected software), second hand bookshops and DVD rentals, and also libraries and museums which acquire works from around the world, will be affected. The Library Copyright Alliance (LCA) filed an amicus curiae brief with the US Supreme Court in support of Kirtsaeng.