There could be certain circumstances where republishing something you've written WOULD be unlawful.

That would arise if someone else owns the copyright to it. The most common would be if you wrote the work in the course of your employment. In that event, it would be a "work made for hire" and the employer would automatically own the copyright.

Alternatively, even if you were the original owner of the copyright, you might have transferred ownership of the copyright to a publisher or client.

For a fascinating example, involving litigation over illustrations of cardinal birds, see "A Case of Variations on a Theme," by Arthur H. Seidel in The Philadelphia Lawyer, Spring 2001.
http://tinyurl.com/Seidel-VariationsOnATheme
and also
http://digitalcommons.lmu.edu/elr/vol14/iss3/2

The factual scenario is that a college student wrote a paper as a classroom assignment. There is NO possibility that the college owns the copyright in that student's work. Attorney Gelman's "work for hire" hypothetical is irrelevant.

Moreover, the statement "republishing YOUR OWN WORK breaks no law ..." is certainly true because under the work for hire doctrine the author of a work created by an employee or one specially commissioned is the hiring party -- not the work's actual creator. The work is not the creator's. On the flip side, like the factual scenario presented by the questioner, the work is owned, and its copyright is owned, by the actual creator when there is no work for hire relationship.

I concur with Mr. Ballard's explanation. My comment was not a criticism of his answer to the question as posed. Rather it sought to be a further exploration of how the pertinent legal principles might apply in different scenarios. This led to the inference that the specific answer he wrote shouldn't be read out of context as being generally applicable to all factual circumstances.

In my own view, the value of a public bulletin board such as this is that it provides an opportunity for us lawyers to educate the public as to the general principles of law applicable to the subject matter of their questions, rather than to provide actionable legal advice as to particular circumstances. The latter is more appropriately delivered confidentially in the context of an attorney-client relationship. The former is the context in which I offered my previous comment.

Well said.