Using coral ethical issues

Does anyone know what the ethical issues are regarding
purchasing/using coral in jewelry? 

That would depend in part on what type of coral, and especially how
and where it was obtained. There are various restrictions on removing
corals from some locations, and with some types, that pretty much
includes all the traditional sources. But other types or locations
may not have restrictions. There isn’t, so far as I know, any sort of
global agreement banning or regulating coral use or trade, as there
is with elephant ivory.

At every gemshow there are piles of it at almost every booth. Is
there a dyed version that is OK 

From what I’ve seen, the majority of that red decorative stuff you
see as tons of various beads at the shows, aren’t actually coral.
It’s a fast growing plant called sea bamboo, if I recall, and the
red (or other) color is dye. True corals of decent quality beyond
tiny beads or small baroque twig beads, are not so common. And some
of what you see is not sea bamboo, but dyed (or occasionally, natural
color) shell, which sometimes can closely resemble some types of
coral. Really good examples of red Mediterranean coral has always
been at least somewhat rare, even before the beds were pretty much
depleted and killed off by pollution. Now, pretty much anything you
find for sale is old stocks, not recently obtained.

Peter