The goal of detecting future events has several implications and two of them are explored in this chapter. First, the objective of detecting future events means that whoever poses a threat has to be targeted and if the threat is posed by a number of individuals that increases over time, enmity is extended to those individuals. This is true even if they act in the name of a terrorist group that did not exist when the conflict started. From a legal perspective, this practice is facilitated by the uncertainties related to the temporal delineation of conflicts. Second, the objective of addressing future threats entails to act against individuals who are not presently perpetrating hostile acts. This practice requires that the traditional interpretation of direct participation in hostilities be subjected to a temporal change. Instead of suspending the protection of civilians solely when ‒ and only for such time as ‒ they engage in acts that reach a certain threshold of harm, targeting enemies because of the threat they pose for the future means extending direct participation in hostilities not only to preparatory acts, but also to signs revealing membership to an enemy group. This shift is facilitated by the insufficiently defined notion of “continuous combat function.”

This chapter considers the function of consent in respect of the international laws on force and intervention, specifically in relation to so-called solicited actions undertaken by so-called third states. How ‘consent’ is implicated in the normative design of both force and intervention is explored by means of an historical assessment that takes on the cognate ideas of coercion and dictatorial interference. The chapter then moves to unpack the ambitions of and limitations for consent set forth more broadly within public international law, principally by analysing three resolutions of the Institut de droit international (IDI): on insurrection, on civil war, and on military assistance. The chapter also undertakes a detailed examination of the significance and mechanics of the operation of consent in other laws of the ius ad bellum (collective self-defence, counter-intervention, pro-democratic intervention, UN Security Council authorisation), quite apart from its role in governing the lawfulness of the practice of solicited action itself.

The past decade has seen outside states, coalitions or regional organisations lead military operations at the (real or alleged) ‘invitation’ of one of the parties embroiled in military strife – notably, in Mali, Syria, Yemen, and The Gambia. This chapter addresses key legal questions, starting with the validity of a government’s ‘consent’. Others include the legal nature and the effects of such consent, and how a government might lose its capacity to consent to military action in its own territory. The chapter includes analysis of the legal doctrines that might limit the lawfulness of the intervention despite such consent, including the invalidity of consent, the ‘negative equality’ doctrine or complete abstention, unlawful purposes, and other grounds of illegality, such as the inviting state’s complicity in international crimes. In the cases examined in the volume, the intervening states typically invoked multiple legal grounds, of which invitation is only one, and the UN Security Council has been intensely involved: the chapter appraises the legal significance of these novel features. It concludes with a summary of the trialogue method and an overview of the subsequent chapters.

Using a classical perspective tending to interpret existing positive international law, this chapter pursues a double objective. First, it fits in with the doctrinal trend embodied by the Institut de droit international (IDI) in emphasising that intervention by invitation is unlawful if it implies interference in an internal situation, contrary to the right of peoples to self-determination. Second, this research highlights the growing role of the UN Security Council in appraising and characterising the conditions surrounding the legal validity of intervention by invitation. The chapter focuses on military operations in Mali (2013), Iraq (2014), Syria (2015), Yemen (2015), and The Gambia (2017). It observes how, by adopting resolutions, the UN Security Council made pronouncements on which authority was entitled to give its consent, and on the legitimacy of the object and effects of the intervention. The chapter concludes that the Council no longer necessarily authorises any military intervention, but centralises and multilateralises the appraisal of the circumstances surrounding the formulation of the invitation.

This concluding chapter draws the central threads of the book together. It proceeds in five steps, providing conclusions, first, on the limitation of military intervention by invitation and, second, on the institutionalisation triggered by the increased importance of the UN Security Council in the operation of the law. It then takes up the question of whether Council practice may contribute to the development of the law, and it addresses the politicisation of the practice of consensual military intervention. Finally, it argues that while practice has been multilateralised as a result of the increased role the Security Council plays, we are in fact witness only to a ‘half-hearted multilateralisation’.

Aiming to move beyond the limited primary sources on which polarised debate is usually based, this chapter reviews new data on UN Security Council practice in response to consensual interventions. From 1990 to 2013, the Council passed resolutions on 76 per cent of all internal conflicts. This chapter evaluates that response in light of four leading theories: of the Court in Nicaragua, that governmental invitations are always valid; of the Institut de droit international (IDI), that pro-government interventions are ‘allowable’ until a conflict becomes a civil war; that intervention is allowable at the invitation of an elected ‘democratic’ government to secure or restore its power; and that it is allowable in response to an invitation to counter ‘terrorist’ threats. The data shows that the Council does not unequivocally support the Nicaragua or IDI views but has approved regularly the anti-terrorist, and occasionally the pro-democracy, views. Its active voice is more marked than its alignment with any one theory. Among other implications, the IDI view – a Cold War response to abuses of supposed invitations – may be less salient when a multilateral check on such abuses is available.