Given the potential perspective for linking cap-and-trade schemes the question may arise, whether such a discrepancies as regards specifying the character of legal rights to compliance units could pose any threat to investors. But taking into account the experiences of the EUETS (consisting in fact of 27 separate national legal regimes), it seems that the harmonisation in that regard isn’t the necessary condition for the market to function properly. The complications may, however, arise on some particular occasions (like the recent thefts from the registries for instance). It could be also presumed that with the developing market the mounting pressure will be observed to harmonise the approach – for the sake of legal certainty and the liquid circulation of emission compliance units.