When he’s enslaved by aliens, a New York mob boss must rally his fellow prisoners, take over the spaceship and teach his captors; even in space, the mob rules.

This reads well but needs a bit of polish.

After he's abducted by alien gangsters, a 1930's liquor smuggler must rally all the other abductees to break out and get back to Earth.

"When he's enslaved by aliens, a New York mob boss must rally his fellow prisoners, take over the spaceship and teach his captors; even in space, the mob rules."

>>>It's also a comedy because they are the stereotypical gangsters of that time. What would have worked for describing him?

I suggest reclassifying it as a comedy because it more accurately conveys the sensibility.

What kind of black market is he to be sold on?? A violent gangster is going to be temperamentally unfit to submit to servitude as a slave.? Of all the people that could be abducted, why would aliens abduct him?