Buck is controlled by Sam Because social or legal expectations or demands that Buck should obey or serve Sam.

Buck is controlled by Sam Because Buck is of a lower class than Sam.

Buck is controlled by Sam Because Buck is a slave or classed as an animal.

Buck is controlled by Sam Because Sam is Bucks parent, spouse or guardian. And the law gives Sam power over Buck.

Buck is controlled by Sam Because The law requires Buck to take responsibility for Sam.

Buck is controlled by Sam Because it is Sam's job to control Buck.

Buck is controlled by Sam Because of family responsibility.