: Another point is that although you may have to do something to
: "register"
: copyright under US law, that isn't necessary under the international
: copyright conventions, or under most countries' implementations of them.
: The fact that copyright is implicit possibly has something to do with
: needing to be seen to take some action to enforce it for it to remain
: useful. No doubt case law differs in each country where you might want to
: take action...

Registration is not required for protection under US law, but it does set the stage for a more vigorous defense. For example you can sue for "statutory damages" not just actual damages. Let say someone infringes on a copyright and it turns out you lost $5,000 in lost sales. Without registering, the most you can hope to get is $5,000. With registration you can seek a penalty of up to $150,000 regardless of your actual losses. It also lets you seek a jury trial which you can not have without registration. Both of these advantages can serve to make your cease-and-desist later much more threatening and effective.

BTW, I'm not a lawyer so all of the above may be wrong, but it is my understanding.