Hostage, a person held in captivity to assure that an agreement is observed or to coerce another party into taking (or not taking) some action. Countries in ancient and medieval times sometimes exchanged hostages, often persons of high rank, who could be put to death if certain agreements were broken. Invading armies often take hostages of local citizens to discourage resistance to their occupation. Terrorists sometimes seize hostages both to force concessions from governments and to gain publicity for their cause.
It's a pretty straightforward question with an obvious answer, right? Well, yes, until you start peering at both federal and state laws. That's when things start to get interesting.
In their own vision of themselves, Yakuza descend from Robin-Hood-like characters who defended villages from bandits. Today, they operate as a collection of criminal gangs.