Essential (or fundamental) or inessential law
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Between "fundamental" and non-fundamental laws.
There is also another distinction of laws into fundamental and not fundamental: but I could never see in any author what a fundamental law signifieth. Nevertheless one may very reasonably distinguish laws in that manner.
For a fundamental law in every Commonwealth is that which, being taken away, the Commonwealth faileth and is utterly dissolved, as a building whose foundation is destroyed. And therefore a fundamental law is that by which subjects are bound to uphold whatsoever power is given to the sovereign, whether a monarch or a sovereign assembly, without which the Commonwealth cannot stand; such as is the power of war and peace, of judicature, of election of officers, and of doing whatsoever he shall think necessary for the public good. Not fundamental is that, the abrogating whereof draweth not with it the dissolution of the Commonwealth; such as are the laws concerning controversies between subject and subject. Thus much of the division of laws.
Hobbes, Lev XXVI 42-3