To their credit, they do seem to make it clear in the ad that this is no easy thing:
US - BUYERS
There are two ways to import this Defender as far as we know, there may be more avenues which we do not know about. You can go through an RI-Registered Importer and pay to convert this truck to meet DOT/EPA certifications. All the glass has DOT stickers just so you know. This may cost about 8-10K depending on who you deal with.
You can also import it as a rolling chassis with the engine out and register it as a self built vehicle. The laws differ on this from state to state. We will help and assist you with any way you choose to go.
Also for US buyers there is a 2.5% duty and broker fee of appx. $250 to cross the border.