Ray Saintonge wrote:
Matthew Brown wrote:

>Michael Snow writes:
>
>>For the types of uses for which US copyright law allows "fair use",
>>
>the Berne Convention 
>
>>requires that the source of the work be mentioned.
>>
>
>A clarification I'd like: does *US copyright law* require the source be
>mentioned?  Or is it the Berne Convention that requires it?
>
Does it matter?   If the United States has ratified the Berne 
Convention, then international law would have it that its provisions 
override contrary provisions in US domestic law.
The requirement is found in Article 10 of the Berne Convention. The United States ratified the Berne Convention effective March 1, 1989. As Ray says, that should make the requirement US law as well. And in any case, I would prefer to see us complying with international law and not relying on the crutch of "Our servers are located in the US, so that's the only law that applies."

There is no independently codified requirement in US copyright law. This is partly because in US copyright law, fair use is handled as a defense claimed by the party accused of copyright infringement. As such, the "fairness" of a use is decided on a case-by-case basis, and the Copyright Act creates no specific requirements for fair use - it only mentions some factors to be considered. The factors mentioned in the Act say nothing either way about mentioning the source, so the problem is not really a contrary provision, just the failure to explicitly incorporate the requirement. I expect that even without considering the Berne Convention, a court might look more favorably on a fair use defendant who acknowledged the source openly.
Nevertheless, the 
United States has often made the claim in many areas that the opposite 
is true, much to the annoyance of other nations.
Indeed, although from the perspective of copyright law, the bigger sticking point has been the moral rights of authors.
Whatever the law, citing sources remains a desirable practice.  The 
ability to trace a submission is the strongest evidence that we can have 
for establishing our rights to do what we do.
I agree with Ray and Jimbo. There are many good reasons to cite sources - as a matter of ethics or just plain courtesy, and as good scholarly practice to improve verifiability. It's good to cover our legal bases as well, but that's hardly the only reason.

--Michael Snow