A summer blockbuster, a best-selling book and some disgruntled once-obscure authors all are playing roles in a legal drama set to climax today with a judge’s ruling in London.

The case: Did “The Da Vinci Code” violate copyright law?

At issue is whether Dan Brown, author of the book that is being made into a movie starring Tom Hanks and set for release next month, illegally snatched ideas originally published 24 years ago by Michael Baigent and Richard Leigh in their nonfiction book, “Holy Blood, Holy Grail.”

Michael Hoeflich, a Kansas University law professor who teaches a course in copyright law, said a win for the plaintiffs could expand copyright claims and clamp down on future literary, cinematic and otherwise artistic endeavors.

Aside from immediate effects – potentially delaying the film’s release and forcing the book’s publisher to pay millions of dollars in royalties – a win by Baigent and Leigh could change the way the law views copyrights.

No longer would a person’s specific expression of an idea be the only thing protected. Such a ruling could find that the idea itself – in this case, the prospect that Jesus married Mary Magdalene and produced a family tree that continues today – could be owned by its writers, producers, painters or others.

Hoeflich notes that William Shakespeare drew many of his ideas from a variety of previously published works before injecting his own magic: The Bard’s gift of language.

“Do we really want a situation where you can’t use others’ ideas?” he said. “If Baigent and Leigh win this case, and another Shakespeare shows up and writes the same way, he can’t do it, because he’ll have to get copyright permission from all the earlier books’ authors.”

But Hoeflich also sympathizes with Baigent and Leigh, who have sold a relative handful of copies of their book, while Brown’s work has lived on the best-seller lists since its release three years ago, now having sold more than 40 million copies.

Copyright law is clear on one thing, Hoeflich said: A person cannot “own” a historical fact. Baigent and Lee apparently understand this, now arguing that their original book essentially is a work of fiction, despite having spent years marketing “Holy Blood, Holy Grail” as nonfiction.

The change is only one of several inconsistencies that make the latest legal tussle a “bad case,” Hoeflich said. Disputed facts and holes in testimony could lead to a ruling so narrow that it would have little legal strength, other than to prompt a slew of future claims both in Great Britain and America.

And make for lively discussion. Hoeflich, who has read both books, recalls having met Baigent while teaching in England and already is making plans to use the case in class next semester.

“Once the DVD comes out, I’ll probably get a copy and show it in my class,” Hoeflich said.