Upholding the first sale doctrine

GPL 3(b): "Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code"

The more interesting case is if the work was originally distributed under 3(a) and you received a binary CD and a separate source CD. Selling the binary CD on its own would cause the recipient to have problems.