Page - 187 - in Loss and Damage from Climate Change - Concepts, Methods and Policy Options

7 LegalResponses toClimateChange… 187 Thisprinciplewas confirmed in further decisionsof international courts and tri- bunals(e.g.CorfuChannel,22;CaseconcerningtheGabcikovo-NagymarosProject, para.53;CaseConcerningPulpMillson theRiverUruguay, paras.101,193 [here- inafter:PulpMills]). Itwasalsorecognisedininternationaldeclarations(e.g.United Nations RioDeclaration on Environment andDevelopment, principle 2; Declara- tion of the UnitedNations Conference on theHuman Environment, principle 21; UNGARes.2996 (XXVII)) and, although less systematically, in treaties, including amention in thepreamble to theUNFrameworkConventiononClimateChange. In theAdvisoryOpinionon theLegalityof theThreatorUseofNuclearWeapons, the InternationalCourtof Justice recognised thegeneralobligationofStates toensure that activitieswithin their jurisdictionandcontrol respect the environment of other States or of areas beyond national control is nowpart of thecorpusof international lawrelating to theenvironment (para29). Theno-harmprinciplerequiresstates torefrainfromengaginginactivitieswhich wouldcausesignificanttransboundaryharmandtopreventpersonsorentitieswithin its jurisdiction to carry out such activities. Beyond this general understanding, the modalities of theno-harmprinciple aredebated.Aswith anycustomarynorm, it is difficult to establish the exact scope of this duty to prevent significant transbound- aryharm. In its previous cases, the ICJhas clarified little the content of theduty to prevent significant transboundaryharm.Generally, it hasbeenunderstoodasoneof duediligence (PulpMills, para101; ILC2001:154,para.7).Thismeans thata state is required to act in away that can be expected from a “good government” (ILC 2001: 155, para. 17) and to exert its best efforts tominimise the risk of significant transboundaryharm(ILC2001: 154, para. 7).As such, theno-harmprinciple is an obligation of conduct, not of result. Thus, a state is not responsible for harm that occurs despite its reasonable efforts to prevent it or—in case that it is not possi- ble—tominimise therisk.TheInternationalLawCommissionhasacknowledged in itsworkon theArticleson thePreventionofTransboundaryHarmfromHazardous Activities thatadifferentdegreeofcareisexpectedfromstateswithfewercapacities andeconomicdifficulties (ILC2001:155,para.17).Whenapplying thiscriterion to climate change, itmust also be kept inmind that treatiesmay contribute in differ- entways to thedevelopmentofcustomary international law.Despite thecontinuing workoftheILContheroleoftreatiesinidentifyingcustomaryinternationallaw(see e.g.Wood2015:14ff), there remainfundamentaluncertaintiesonhowthemultilat- eral environmental agreements shape,crystalliseandformthecontentofcustomary international law. Statepracticeandcaseswhere theno-harmrulewas invokedgenerallydealtwith activitiesatoraroundasharedborder.Theseactivitiesincludedforinstanceemitting toxicfumesthatcauseddamagesinthewoodsof theneighbouringstate,dredgingin a shared river andaltering itswaters (e.g.LacLanouxArbitration)or elsepolluting it throughmills (e.g.PulpMills)orconstructionactivitiesclose to it.This raises the questionwhether theno-harmprinciple is applicable toclimatechange. Climate change differs frommost aforementioned cases in at least three pivotal points.Firstly,damagesfromclimatechangeresultnotfromasingleactivityofastate