Difficult as it might be to discern, this isn't a story from The Onion. According to this article by Matt Danzico and Kate Dailey in BBC News Magazine, while "Republican candidates in Nevada were debating such American issues as nuclear waste disposal and the immigration status of Mitt Romney's gardener", American and British lawyers in Philadelphia were checking whether Jefferson's Declaration of Independence was legal.
The Declaration of Independence was not only illegal, but actually treasonable. There is no legal principle then or now to allow a group of citizens to establish their own laws because they want to. What if Texas decided today it wanted to secede from the Union?
Lincoln made the case against secession and he was right. The Declaration of Independence itself, in the absence of any recognised legal basis, had to appeal to "natural law", an undefined concept, and to "self-evident truths", that is to say truths for which no evidence could be provided.