Is re-selling used books a violation of copyright laws?

How does it differ from sharing DRM'ed e-books?
Used bookstores are a
very big business in tourist vacation locales of Third World countries. Pretty big in some First World countries too. In some beach resorts one can find 2-3 used bookstores on each block of the main streets. All the latest best-sellers line the windows, and are sold for just a dollar or two. Obviously neither the author nor publisher make any money from this, and just as obviously these books are still under copyright protection. A large percentage of these books are actually NOT even
used, but produced in Cambodia, the capital of pirated book production.
Many of these same countries that actively prohibit pirated computer software, pirated DVD's of both music and movies, and copied designer clothing and handbags, etc., don't seem to make any efforts towards used bookstores. Why?
Stitchawl