Justice Jackson's dissent in Terminiello v. City of Chicago, 337 U.S. 1 (1949):
This Court has gone far toward accepting the doctrine that civil liberty means the removal of all restraints from these crowds and that all local attempts to maintain order are impairments of the liberty of the citizen. The choice is not between order and liberty. It is between liberty with order and anarchy without either. There is danger that, if the Court does not temper its doctrinaire logic with a little practical wisdom, it will convert the constitutional Bill of Rights into a suicide pact.
A ELU user explained it:
The phrase "The Constitution is not a suicide pact" contends that the civil rights guaranteed under a constitution (the U.S. Constitution specifically, but I suppose it could apply to any constitution) should not be construed in such a way as to enable the destruction of the society it governs.
But I still don't understand the relevance or metaphor of 'suicide pact'. What/Who metaphorically has agreed to suicide? How've they agreed? What is the 'suicide'? 'Destruction of the society' isn't necessary suicide, e.g. if it's something not agreed that destroys (e.g. civil war, nuclear weapons accident).