I don't think it's possible to justify all the plot holes and internal contradictions in the six Star Wars movies, particularly those in the, ahem, less-than-stellar, Episodes I-III. However, this is an interesting effort to address at least some of them (hat tip:co-blogger Tyler Cowen). In particular, the author explains how it is that Chewbacca is a high-ranking Wookie leader in Episode III, yet has fallen to the level of a sidekick for an impecunious smuggler by the time of Episode IV.
However, there are just far too many holes in the Stars Wars for even the most impressive Jedi mind tricks to patch up. This analysis ignores two of the biggest ones:
1. At the end of Episode III, Obi-Wan and Yoda try to hide the existence of the twin children from their father, Darth Vader. Unless they have gone over to the Dark Side themselves, why would the supposedly wise Jedi masters even consider "hiding" Luke with his uncle and aunt (Vader's only living relatives, so far as he knows) on Tatooine (Vader's home planet) and having the child live under his own name? It's as if Osama Bin Laden tried to hide from Bush by renting an apartment under his own name next door to the Bush ranch in Crawford, Texas. Hiding Leia with Senator Bail Organa on Alderaan seems smart by comparison, but it's pretty boneheaded as well. Organa is a prominent political opponent of the Emperor's and he's going to be under constant surveillance by the Empire even if they don't suspect that he's hiding one of Vader's children. Given that the Sith can detect even latent force abilities at a great distance, Leia should have been found very quickly indeed (though not as fast as Luke!).
2. Given the above, it's totally inexplicable that the Emperor and Vader fail to find the two children in the twenty-plus years that pass between Episode III and Empire Strikes Back. In the original Star Wars, Vader even interrogates and mind-probes Leia, but still fails to figure out that she is his daughter, or even that she has Force abilities (even though in Episode I and Return of the Jedi we learn that any competent Jedi or Sith can detect such abilities even at a great distance). The Emperor and Vader were either 1) complete morons (In which case, who would want to bring back a Republic so pathetic it could be overthrown by the likes of them?) 2) actively trying to sabotage their own government, or 3) handicapped by an incompetent screenwriter.
Although clever and original, this Chewbacca defense will convince only the weak-minded.
For a more comprehensive takedown of the Stars Wars movies, see these essays by science fiction writer David Brin. To paraphrase Darth Vader, Brin is not as forgiving of Star Wars as I am.
UPDATE: Although I ultimately don't agree with most of their points, I am impressed with the ingenuity of many of the commenters who have made valiant efforts to defend George Lucas' handiwork and reconcile the seeming inconsistencies. I wish that I could get law students to work this hard on analyzing case law:).
In the end, however, the big problem with elaborate, after-the-fact explanations of the plot holes in Star Wars is that there is little if any hint of these explanations in the movies themselves. For example, if it is indeed true that Vader failed to detect Luke over the twenty year period from the Episode III to the Empire Strikes Back because he deliberately broke off all connection with Tatooine and his old family, it would be nice if there was at least a brief line in which Vader or someone else says so. To my mind, a plot hole that can only be explained away through an elaborate post hoc rationalization that is not mentioned in the film itself, is probably a hole that can't be explained at all.