Could Goku have been revived if he really wanted, after dying fighting Cell? After defeating Cell, they revived all his victims using Shenron. But Shenron could not revive Goku, as he already revived once. Then, Goku contacted them using King Kai's telepathy and asked them not to revive him. 

The question is, would it have been possible to revive him somehow (at that point of the story) if he were not against it?
Unlike the Dragon Balls on Earth, the Dragon Balls of Namek are not restricted to reviving someone once. During the fight with Kid Buu, Goku and all the people Buu killed on Earth as well as the planet itself were revived by having the Namekians collect the Dragon Balls.

So yes, Goku could and was revived again by the Namekian Dragon Balls.