States clearly possess, or at least claim to possess,political power. The sociologist Max Weber (1864-1920) made a similar point, if in more startling language: states possess a monopoly of legitimate violence. Within any state, violence or coercion is seen as primarily the state's business, either directly, through its agents—the police and law courts—or indirectly, through the permissions it gives citizens to be violent to each other on occasion: in self defence, for example. All legitimate violence or coercion is undertaken or supervised by the state.
An Introduction to Political Philosophy, pg. 36
I'm taking Political and Social Philosophy this semester, and this is from one of the textbooks we'll be using. So far, it's quite interesting. Hopefully, the class itself will be at least as interesting.
ADDENDUM: This article at Positive Liberty goes well with this quote.