Can Articles 144 and 86 of Council Directive 2006/112/EC be interpreted to mean that the only condition in order for connected services consisting of the ‘inbound' transport service — from airports to the place of destination within the territory of the Member State, with the ‘free-at-destination' clause — not to be liable to VAT is that their value is included in the taxable amount, regardless of whether or not the goods in question were in fact subject to customs duties, at the time of their importation; and is it therefore incompatible with those EU-law provisions if the domestic rules laid down in Articles 9(1).2 and 69(1) of Presidential Decree No 33 of 26 October 1972, read together in the versions in force at the time of the material facts, provide that in every case, and therefore also in the case of imports that are not liable to VAT — as is the case here, since it concerns documents and goods of negligible value — there has to be compliance with the additional requirement that those imports must in fact be liable to VAT (and customs duty must in fact be paid) at the time of the importation of such goods, even, if need be, when account is taken of the ancillary nature of the transport services in relation to the main services (namely the importation) and of the rationale of simplification underlying both the main and the ancillary operations?