No worries, man...
Unfortunately clams are listed on CITES ("convention on international traffic in endangered species" or something like that, see
www.cites.org for more info) which means you need a CITES permit to bring them over legitimately. There's actually nothing stopping a person from getting a permit, it's just that it's probably a bit much effort and money for just one thing or two.
In the end it's probably a good thing to try and protect/control the movements of endangered species, but it does make it a pain for us little guys. When I was in Detroit a few years back (a total hotbed of reefing activity, who knew????) I saw some
amazing clams at
www.tropicorium.com, the likes of which I have never seen since. Oranges, black maximas, turquoises .... Let me tell you it was a hard thing to pass up!! .... sigh. Oh well...