Government has a monopoly on the legitimate use of force.
Weber claims that the state is the "only human Gemeinschaft which lays claim to the monopoly on the legitimated use of physical force. However, this monopoly is limited to a certain geographical area, and in fact this limitation to a particular area is one of the things that defines a state."[2] In other words, Weber describes the state as any organization that succeeds in holding the exclusive right to use, threaten, or authorize physical force against residents of its territory. Such a monopoly, according to Weber, must occur via a process of legitimation.
https://en.wikipedia.org/wiki/Monopoly_on_violence
This is mis-read by many Libertarians, including Charles Koch,[1] who directly funds a wide set of Libertarian institutional propaganda mills,[2] that this invalidates government. It does not.
Absent a monopoly, there are multiple parties that claim legitimacy over use of force, including lical strongmen, tribes, or corporations, for all of which there is an extensive history of same (including Koch Industries, to the present).
Government's monopoly is not for unlimited use of force, but for legitimate use.
And if some alternate structure emerges claiming this right, it is, ipso facto, government.
It is also possible for actual or nominal governments' use of force to be illegitimate. Which it rather frequently is.
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Notes:
1. https://www.marketplace.org/2015/10/21/business/corner-offic...
2. Amply documented, see: https://en.wikipedia.org/wiki/Political_activities_of_the_Ko... https://www.sourcewatch.org/index.php/Koch_Brothers