In his main work "Homo Sacer: Sovereign Power and Bare Life" (1998), Giorgio Agamben analyzes an obscure^[26] figure of Roman law that poses some fundamental questions to the nature of law and power in general. Under the Roman Empire, a man who committed a certain kind of crime was banned from society and all of his rights as a citizen were revoked. He thus became a "homo sacer" (sacred man). In consequence, he could be killed by anybody, while his life on the other hand was deemed "sacred", so he could not be sacrificed in a ritual ceremony.

Roman law no longer applied to someone deemed a Homo sacer, although they would remain "under the spell" of law. Agamben defines it as "human life...included in the juridical order solely in the form of its exclusion (that is, of its capacity to be killed)". Homo sacer was therefore excluded from law itself, while being included at the same time. This figure is the exact mirror image of the sovereign (basileus) — a king, emperor, or president — who stands, on the one hand, within law (so he can be condemned, e.g., for treason, as a natural person) and outside of the law (since as a body politic he has power to suspend law for an indefinite time).

Giorgio Agamben draws on Carl Schmitt's definition of the Sovereign as the one who has the power to decide the state of exception (or justitium), where law is indefinitely "suspended" without being abrogated. But if Schmitt's aim is to include the necessity of state of emergency under the rule of law, Agamben on the contrary demonstrates that all life cannot be subsumed by law. As in Homo sacer, the state of emergency is the inclusion of life and necessity in the juridical order solely in the form of its exclusion.^{[clarification needed]}

Since its origins, Agamben notes, law has had the power of defining what "bare life" — zoe (Gk. ζωή), as opposed to bios (Gk. βίος): qualified life — is by making this exclusive operation, while at the same time gaining power over it by making it the subject of political control. The power of law to actively separate "political" beings (citizens) from "bare life" (bodies) has carried on from Antiquity to Modernity — from, literally, Aristotle to Auschwitz. Aristotle, as Agamben notes, constitutes political life via a simultaneous inclusion and exclusion of "bare life": as Aristotle says, man is an animal born to life (Gk. ζῆν, zen), but existing with regard to the good life (εὖ ζῆν, eu zen) which can be achieved through politics.^[27] Bare life, in this ancient conception of politics, is that which must be transformed, via the State, into the "good life"; that is, bare life is that which is supposedly excluded from the higher aims of the state, yet is included precisely so that it may be transformed into this "good life". Sovereignty, then, is conceived from ancient times as the power which determines what or who is to be incorporated into the political body (in accord with its bios) by means of the more originary exclusion (or exception) of what is to remain outside of the political body—which is at the same time the source of that body's composition (zoe).^[28] According to Agamben, biopower, which takes the bare lives of the citizens into its political calculations, may be more marked in the modern state, but has essentially existed since the beginnings of sovereignty in the West, since this structure of ex-ception is essential to the core concept of sovereignty.^[29]

Agamben would continue to expand the theory of the state of exception first introduced in "Homo Sacer: Sovereign Power and Bare Life", ultimately leading "State of Exception" in 2005. During 2003, he delivered a lecture at European Graduate School describing the eclipse that politics has undergone.^[30] Instead of leaving a space between law and life, the space where human action is possible, the space that used to constitute politics, he argues that politics has “contaminated itself with law” in the state of exception. Because “only human action is able to cut the relationship between violence and law”, it becomes increasingly difficult within the state of exception for humanity to act against the State.^[