Lastly, an alternative basis for establishing jurisdiction is sometimes found in the effect principle, according to which a state has jurisdiction over acts that, while taking place outside its territory, nevertheless have an impact on it.<sup>71</sup> In the context of carbon pricing in the maritime sector, the effect principle could provide a legitimate basis for jurisdiction because mitigating climate change is a primary interest of single states and the international community as a whole. Note that the effect principle could provide a legitimate basis for both port-state jurisdiction over vessels and jurisdiction over consignees/consignors, and thus potentially for all types of measures considered here, regardless of whether the accounting unit is the cargo or the vessel.

However, contrasting views exist on whether the effect principle could provide a legitimate basis for extraterritorial jurisdiction. Some authors argue that the interest of a state in regulating GHG emissions from shipping on the high seas is weak because the state would be acting as the procurator for a global interest.<sup>72</sup> However, this interest (or the appropriate way of protecting it) is not supported by other states, as testified by the absence of an international agreement on the matter.<sup>73</sup> In support of this conclusion, it has been pointed out that the effect principle has mainly been adopted in antitrust law and is not widely acknowledged in maritime law.<sup>74</sup> Kopela reaches a similar conclusion but on different grounds. In particular, she argues that the effect principle is not foreign to environmental and maritime law.<sup>75</sup> Yet, the application of the principle requires that an activity has a substantial ascertainable impact on the interests of the state. However, in the case of climate change, this impact might not be easily identified.<sup>76</sup> Ringbom sees the uneasy identification of the effect of carbon emissions from the maritime sector on the interests of a state as a potential constraint on the application of the effect principle, but not necessarily an insurmountable one.<sup>77</sup> In this respect, it has been argued that, if the price applied to the emissions reflects the share of the harm suffered by the state, the effect principle could become a more legitimate basis for extraterritorial jurisdiction.<sup>78</sup> The overall conclusion is that it remains a contested issue whether the effect principle could provide a basis for port-state jurisdiction over emissions released beyond territorial waters, but the limitation of the price of carbon to the harm suffered by the state that imposes the measure is likely to strengthen its jurisdictional claim.<sup>79</sup> To conclude this section, the existing literature recognizes various ways of establishing jurisdiction over emissions released in international waters, but none of these options is uncontested and, apart from the effect principle, each of them could potentially apply only to a sub-set of the measures considered here. However, without taking a position on which (if any) of these approaches would be more legitimate, this paper highlights that, historically, regional action has served as a basis for the expansion of states’ jurisdiction under maritime law.<sup>80</sup>

# **_3.2 Availability of Data_**

A key issue related to the implementation of carbon pricing in the maritime sector is the limited amount of emissions data available to the public authorities. The data needed for carbon pricing, and the corresponding obstacles to obtaining it, are likely to vary depending on the design of the measure. The literature has identified several approaches to resolving this data problem.

> 71 E.g. Bäuerle et al. (2010, pp. 85-86).

> 72 Hermeling et al. (2017, pp. 16-17). Against this conclusion, it has been argued that a state can legitimately act for the protection of a global interest when such interests are in line with the aims and obligations set out in international instruments; see Kopela (2016, p. 110).

> 73 Hermeling et al. (2017, pp. 16-17).

> 74 Hermeling et al. (2017, p. 16).

> 75 Kopela (2016, p. 107).

> 76 Kopela (2016, p. 107).

> 77 Ringbom (2011, pp. 630-631).

> 78 Heine et al. (2017, p. 39); Heine and Gäde (2018).

> 79 Heine et al. (2017, p. 39); Heine and Gäde (2018).

> 80 See, for instance, Boyle, (2006, p. 17). See also below, Section 5.

9