>The fact that a film might be 'public domain' in the US means >absolutely nothing in relation to rights issues relating to >exhibition in other countries.

Don't mean to be contrary but this isn't exactly true.  Under the Berne Convention, any signatory nation grants the same copyright protection to foreign works copyrighted in their nation of origin as that first nation would to any native work.  For instance, for any US film with proper US copyright then New Zealand would give that film the same copyright protection it would to a NZ film (which of course might not be the same as the US:  Italy and Japan have--or had--shorter copyright periods so some works go into public domain more quickly there).

So a US film that's in the public domain in the US generally speaking would not be protected by copyright in New Zealand.  It's possible (but unlikely) that NZ law does indeed grant some kind of protection (such as moral rights) to foreign works not covered by Berne but that would be a country-by-country situation.  What may be confusing about this is that a person with a valid copyright can sell rights to the work in different countries but if the work is public domain then there are no rights to sell.

The text of Berne is at http://www.law.cornell.edu/treaties/berne/overview.html

----
Online resources for film/TV studies may be found at ScreenSite
http://www.tcf.ua.edu/ScreenSite