Dragonback
Book 5: Dragon And Judge

Orphaned at the age of three, brought up by his Uncle Virgil, a con man, Jack Morgan has done things that are unusual even in the future in space. But when he rescued Draycos, a dragon-like symbiont, from certain death, his life became a series of breathtaking adventures.

With the help of Draycos, who can leap onto Jack's back and become what looks like a tattoo, Jack has been doing everything he can to find out who ambushed the scout-fleet of Draycos's people, the K'da and Shontine, leaving Draycos the sole survivor. Now Jack thinks he may finally be on the trail of the information he needs.

But before he can act on what he knows, he's kidnapped by aliens, who ask him to be a judge for them, as, they reveal to him, his parents had once been.