For John Howard Yoder, it is axiomatic that Christians ethics is for Christians; proposed alternatives tend to fall prey to unbelieving modes of moral discernment, whether Constantinian (thinking morally first of all from the position of the powerful) or Kantian (thinking morally first of all from what can be demanded of everyone).
This position is often taken to be sectarian, and therefore apolitical: the church does its thing, the state does its thing, and Christians accordingly have nothing to say to or to expect of the state.
This reading, however, confuses implementation and validation.
Implementation, on the one hand, names the actual possibility that the state, when addressed by the church (as the church is called in its life of witness to do in word and deed) to obey the form of life revealed in Christ as the will of God, really is able to respond, for whatever reason and in whatever way, in agreement with and enactment of the church's address. Hence: non-Christian or secular appropriations of Christian initiatives such as communal meetings of open dialogue, institutions for care of the sick, nonviolent resistance of oppression, privileging of the underdog, and so on.
Validation, on the other hand, names the (often unspoken) philosophical expectation or demand that Christian ethics be both applicable to and practicable for every person in any given society (including the ruler and the nonbeliever); if it fails this test, it is thereby rendered invalid. Yoder explicitly and vehemently rejects this approach to the so-called "relevance" or "responsibility" of Christian ethics, revealing it for what it is: a smokescreen for disallowing radical discipleship to be seriously expected of all who claim to be disciples, on the false grounds that it only "applies" to a "sect" -- for "we know" that the gospel is "political" and so concerns "everybody" and includes "all realms of life."
Indeed, the gospel is political and does concern all people and realms of life -- but in a peculiar way consistent with its own message and practice. Thus construed, Christian ethics, as the form of life of that particular people in the world called the church, constitutes a concrete and viable offer to the world which the world may in fact adopt, adapt, or otherwise appropriate. Whether or not the world does so, and in what way and for which reasons, bears no relation whatsoever either to the substance of the gospel's moral vision or to the expectation that the church obey it. To assume or allow such a determining relationship would be to presuppose that the world's internal possibilities encapsulate and so confirm or invalidate the command of God in Jesus Christ, rather than -- as Scripture and as Yoder so emphatically insist -- the other way around.