user-1: The closing of this Where can I find spanish subtitles for Dragon Ball legally? question suggests that unofficial subtitles are illegal. 
Is this true?

user91: Translation is considered a "derivative work" and those can only be made by the copyright owner of the original work. Rights to create derivative works can be sold/given/granted to others at the whim of the copyright owner of the original work.

http://www.technollama.co.uk/are-fan-translations-an-infringement-of-copyright


Subject to the limitations prescribed hereinafter, copyright shall include the exclusive right to exploit the work by making copies of it and by making it available to the public, be it in the original or an altered manner, in translation or adaptation, in another literary or artistic form, or in another technical manner.


http://www.copyrightkids.org/copyrightbasics.html


In general, it is illegal for anyone to do any of the things listed above (make translations) with a work created by you without your permission


http://www.legalzoom.com/intellectual-property-rights/copyrights/what-are-derivative-works-under


A derivative work is a new, original product that includes aspects of a preexisting, already copyrighted work. Also known as a "new version," derivative works can include musical arrangements, motion pictures, art reproductions, sound recordings or translations. They can also include dramatizations and fictionalizations, such as a movie based on a play.
Only copyright owners have the exclusive right to produce derivative works based on their original, copyrighted works. Copyright on original works of authorship is automatic, and registration—while it does carry significant benefits, like the right to sue for infringement—is not required for a work to be protected; protection attaches immediately when the work is completed.

Some countries may not honor international copyright law, but most places do and the copyright on derivative works apply internationally.

user1530: Briefly:
Subtitles are treated much like movie scripts by most video industries, that is - either downloading user-generated or official subtitles without the copyright holder's consent is subject to intellectual property rights.
Previous Cases:
This said, there haven't been many arrests for people distributing subtitles, the main target of the companies are to prevent copies of video from being illegally distributed.
There have been a couple of arrests though, in countries such as Norway, Israel & France.

NorSub, a site for Norwegian subtitles had to cease operating after a court case from film distributors in the U.S.

Warner sues several different subtitling sites


Legal Stuff:
Most countries are signatories of the Berne Convention, Which in a nutshell, means that national copyright laws apply in international areas for that work:

Before the Berne Convention, national copyright laws usually only applied for works created within each country. So for example a work published in United Kingdom by a British national would be covered by copyright there, but could be copied and sold by anyone in France.

Some example breaches of copyright law (This instance is in the U.S.):

The maker of any copyrighted work, or the owner of that copyright, has the sole right to alter it, and others who modify a work are in violation of U.S. Code Title 17, §102 and §106. These sections guarantee the maker of the work the sole right to make alterations and additions to his work. Because adding subtitles is an alteration of the original product created by the studio, translators must seek permission from the copyright holder before adding foreign-language subtitles to a video.
USC §17-103 also grants copyright holders the sole right to produce derivative works based upon an original film. These derivative works include making-of videos, adding additional audio commentary tracks, or annotating the film. Translations, whether they're performed through dubbed audio tracks or by subtitles, are protected derivative works according to this legislation.
Videos where home users add foreign-language subtitles or close captioning to the original may be protected by personal use limitations if they are not sold or otherwise distributed beyond the household of the person who changed them. Personal use exceptions do not allow consumers to pass along "trial" copies to others for "sampling" purposes or to distribute altered copies even when they don't financially gain from the distribution of those works.

Reference
Should They Be Legal?
Rick Falkvinge, founder of Sweden’s Pirate Party has voiced his support for fan made subtitles. On his website he writes:

“Fan-subbing is a thriving culture which usually provides better-than-professional subtitles for new episodes with less than 24 hours of turnaround, whereas the providers of the original cartoon or movie can easily take six months or more.”

Some other smaller groups have spoken out about the topic also, but as of this moment downloading subtitles are illegal and will probably remain so for a good while.

-1: <p>The closing of this <a href="https://anime.stackexchange.com/questions/6703/where-can-i-find-spanish-subtitles-for-dragon-ball">Where can I find spanish subtitles for Dragon Ball legally?</a> question suggests that unofficial subtitles are illegal. </p>

<p>Is this true?</p>
 91: <p>Translation is considered a &quot;derivative work&quot; and those can only be made by the copyright owner of the original work. Rights to create derivative works can be sold/given/granted to others at the whim of the copyright owner of the original work.</p>
<ul>
<li><a href="http://www.technollama.co.uk/are-fan-translations-an-infringement-of-copyright" rel="nofollow noreferrer">http://www.technollama.co.uk/are-fan-translations-an-infringement-of-copyright</a></li>
</ul>
<blockquote>
<p>Subject to the limitations prescribed hereinafter, copyright shall include the exclusive right to exploit the work by making copies of it and by making it available to the public, be it in the original or an altered manner, in <strong>translation</strong> or adaptation, in another literary or artistic form, or in another technical manner.</p>
</blockquote>
<ul>
<li><a href="http://www.copyrightkids.org/copyrightbasics.html" rel="nofollow noreferrer">http://www.copyrightkids.org/copyrightbasics.html</a></li>
</ul>
<blockquote>
<p>In general, it is illegal for anyone to do any of the things listed above (make translations) with a work created by you without your permission</p>
</blockquote>
<ul>
<li><a href="http://www.legalzoom.com/intellectual-property-rights/copyrights/what-are-derivative-works-under" rel="nofollow noreferrer">http://www.legalzoom.com/intellectual-property-rights/copyrights/what-are-derivative-works-under</a></li>
</ul>
<blockquote>
<p>A derivative work is a new, original product that includes aspects of a preexisting, already copyrighted work. Also known as a &quot;new version,&quot; derivative works can include musical arrangements, motion pictures, art reproductions, sound recordings or translations. They can also include dramatizations and fictionalizations, such as a movie based on a play.</p>
<p>Only copyright owners have the exclusive right to produce derivative works based on their original, copyrighted works. Copyright on original works of authorship is automatic, and registration—while it does carry significant benefits, like the right to sue for infringement—is not required for a work to be protected; protection attaches immediately when the work is completed.</p>
</blockquote>
<p>Some countries may not honor international copyright law, but most places do and the copyright on derivative works apply internationally.</p>
 1530: <h2>Briefly:</h2>
<p>Subtitles are treated much like movie scripts by most video industries, that is - either downloading user-generated or official subtitles without the copyright holder's consent is subject to intellectual property rights.</p>
<h2>Previous Cases:</h2>
<p>This said, there haven't been many arrests for people distributing subtitles, the main target of the companies are to prevent copies of video from being illegally distributed.</p>
<p>There have been a couple of arrests though, in countries such as Norway, Israel &amp; France.</p>
<ul>
<li><p><a href="http://extratorrent.cc/article/2220/subtitles+might+be+illegal.html" rel="nofollow noreferrer">NorSub</a>, a site for Norwegian subtitles had to cease operating after a court case from film distributors in the U.S.</p>
</li>
<li><p><a href="http://torrentfreak.com/anti-piracy-action-closes-yet-more-fansub-sites-090301/" rel="nofollow noreferrer">Warner</a> sues several different subtitling sites</p>
</li>
</ul>
<h2>Legal Stuff:</h2>
<p>Most countries are signatories of the <a href="http://en.wikipedia.org/wiki/Berne_Convention_for_the_Protection_of_Literary_and_Artistic_Works" rel="nofollow noreferrer">Berne Convention</a>, Which in a nutshell, means that national copyright laws apply in international areas for that work:</p>
<blockquote>
<p>Before the Berne Convention, national copyright laws usually only applied for works created within each country. So for example a work published in United Kingdom by a British national would be covered by copyright there, but could be copied and sold by anyone in France.</p>
</blockquote>
<p>Some example breaches of copyright law (This instance is in the U.S.):</p>
<blockquote>
<p>The <strong>maker of any copyrighted work, or the owner of that copyright,</strong> has the sole right to alter it, and others who modify a work are in violation of U.S. Code Title 17, §102 and §106. These sections guarantee the maker of the work the sole right to make alterations and additions to his work. Because adding subtitles is an alteration of the original product created by the studio, translators must seek permission from the copyright holder before adding foreign-language subtitles to a video.</p>
<p>USC §17-103 also grants copyright holders the <strong>sole right</strong> to produce derivative works based upon an original film. These derivative works include making-of videos, adding additional audio commentary tracks, or annotating the film. Translations, whether they're performed through dubbed audio tracks or by subtitles, are protected derivative works according to this legislation.</p>
<p>Videos where home users add foreign-language subtitles or close captioning to the original may be protected by personal use limitations <strong>if they are not sold or otherwise distributed beyond the household of the person who changed them.</strong> Personal use exceptions do not allow consumers to pass along &quot;trial&quot; copies to others for &quot;sampling&quot; purposes or to distribute altered copies even when they don't financially gain from the distribution of those works.</p>
</blockquote>
<p><a href="http://www.ehow.com/list_6799201_copyright-laws-adding-subtitles-movies.html#ixzz2pKzAGjJZ" rel="nofollow noreferrer">Reference</a></p>
<h2>Should They Be Legal?</h2>
<p>Rick Falkvinge, founder of Sweden’s Pirate Party has voiced his support for fan made subtitles. On his website he writes:</p>
<blockquote>
<p>“Fan-subbing is a thriving culture which usually provides better-than-professional subtitles for new episodes with less than 24 hours of turnaround, whereas the providers of the original cartoon or movie can easily take six months or more.”</p>
</blockquote>
<p>Some other smaller groups have spoken out about the topic also, but as of this moment downloading subtitles are illegal and will probably remain so for a good while.</p>
