The case tied 4-4 so effectively upheld a lower court ruling without setting precedent, but the short of it is that IP (copyright) trumps first sale.
Synopsis: Costco was buying watches overseas and selling them in the U.S. Because the logo on the watch was copyrighted, this violated the copyright and thus Costco is barred from selling the watches. The argument is that applying the first sale doctrine to products not made in the U.S. would be enforcing U.S. laws on a foreign nation.
And guess what's not made in the U.S. anymore? Well, pretty much everything...