If it is complex/original enough to qualify then generally yes, the person modifying also has rights on the result. A typical example would be a translation of a text.

EDIT: apparently this is not true for the US, I briefly checked but apparently missed something, my bad. It is for example in Germany.

No, legal derivative works can only be made with the authorization of the copyright holder[1]. The question was specifically about an unauthorized derivation.

Creating any unauthorized derivative work is illegal and thus ineligible for copyright protection, including the preparation of unauthorized translations (other than under fair use exemptions such as for news reporting, research, or scholarly purposes).[2]

[1] https://www.law.cornell.edu/uscode/text/17/106 [2] http://www.unc.edu/~unclng/copy-corner73.htm

As I understand it, there are two different issues, copyright in the derivative work, and legality of the act of creating the derivative work.

Copyright of a derivative work that itself meets the standard for copyrightability rests with the creator of the derivative, because, under law, any copyrightable work has a copyright that belongs to the creator at the moment it is created.

A derivative created without proper permission is also a violation of the copyright of the original, but that's a separate issue.

Just saw your other comment and edited, apparently I didn't check thoroughly enough for the US (Here in Germany the permission isn't needed in most cases. Without permission you can't do much with your derivative work afterwards of course)

how can people do these kinds of work on a speculative basis then? surely their work is protected by copyright even though if they were to reproduce it, it would be infringing. I am sure it's in their copyright when they try to sell it to the company they've derived it from.

otherwise how could anyone do spec work!

EDIT: I mean unsolicited spec work - the company they're pitching doesn't even know they're pitching them until they send their pitch. Surely their pitch is still protected by copyright, even though as it's unauthorized the person producing it wouldn't have the right to publish their pitch without approval (if it's a derivative of the company's assets)?

In general, no, such an unauthorized copy is not legally a derivative work, and therefore the pirate cannot claim any rights over it -- according to 17 U.S.C. § 106[1], derivative works can only be made by or with the authorization of the owner of the copyright.

Adding substantial new content does qualify it as an derivative work -- but it's still infringing, since any derivative works made without authorization are illegal.

[1] https://www.law.cornell.edu/uscode/text/17/106

You seem to be making an unjustified leap that an unlicensed work is ineligible for copyright protection.

If I create a derivative work, e.g., a Star Trek "fanfic", I may not have rights to publish that work commercially, because of the copyright of creator of the base work.

However, the original copyright holder cannot simply take my work and publish it, because I have rights in my own creation.

This leaves the derived work in an awkward position where it cannot be published commercially without consent of both parties, or until expiration of the copyright on the original work (if that ever happens again).