Why didn't Jinbe and Ace wear prisoner uniforms? Ivankof and the others also didn't wear a uniform, but they're part of some kind of underworld society, so they're basically running away; but Jinbe and Ace are prisoners, so why they didn't wear uniforms?

Jinbe



Ace
Jimbei was officially a Shichibukai until he verbally told to Sengoku at Marineford that he is resigning. He was imprisoned just because he didn't follow World Government orders. So there is no reason why he should be wearing prison uniform as he was not a convict.

As for Ace, I think kaine must be right. It must be like when Gol. D Rodger was not in uniform when executed. A likely minor courtesy afforded those waiting execution could be the right to wear their own clothes for their final hours.