Rondor Music, which owns the copyright to the Beach Boys' "California Girls," has sent a letter to Capitol Records demanding that it grant writing credits and royalties for the Katy Perry summer hit "California Gurls" to Brian Wilson and Mike Love, the writers of the 1965 classic.

No one would mistake Perry's song -- which topped the Billboard Hot 100 for six straight weeks in June and July -- for "California Girls." But at the end of "Gurls," rapper Snoop Dogg says, "I really wish you all could be California girls" -- not far off from "I wish they all could be California girls" in the Beach Boys' refrain.

Other artists have paid tribute to "California Girls." Paul McCartney has explained that the 1968 Beatles tune "Back in the USSR" ("Well the Ukraine girls really knock me out/They leave the West behind") was written as "a kind of Beach Boys parody." And country star Gretchen Wilson's own "California Girls" mocked the Beach Boys' coastal female ideal, celebrating inland California's "good women from Sacramento to Corona," while singing, "Ain't you glad we ain't all California girls/Ain't you glad there's still a few of us left, who know how to rock your world."

There isn't any indication that Universal Music Publishing Group-owned Rondor will sue. Indeed, Love and Wilson have said publicly that they like Perry's song. Capitol parent EMI Music doesn't seem to be too worried. "There's no merit to it," EMI spokesman Dylan Jones says.

Still, there's no doubt that Rondor is taking this seriously. "Using the words or melody in a new song taken from an original work is not appropriate under any circumstances," a Rondor spokesman says, "particularly from one as well-known and iconic as 'California Girls.'"

Did Rondor have a legal basis to make its demand? Its blanket insistence that using snippets from others' works "is not appropriate under any circumstances" ignores various potential legal defenses. But, like so many things in the law, it's not an absolute slam-dunk. Underlying any consideration of the legal case is the venerable maxim "de minimis non curat lex": The law doesn't concern itself with trifles. In other words, judges don't waste their time over trivial matters, like copying tiny portions of others' works.

The Copyright Office takes the position that "short phrases or expressions" aren't protected by copyright, even if those short phrases are "novel or distinctive." But the case law is not so clear about how short is too short to merit protection under the law, or when a short phrase is so original and important to the work that copying requires permission.

For example, one appellate court found that the line "Good morning, Detroit. This is J.P. on JR in the A.M. Have a swell day" from the 1987 film "The Rosary Murders" was an unprotectable short phrase because it was "not an integral part of the movie; it was merely an incidental part of the background."

But another appeals court suggested that the phrases "Euclid alone has looked on beauty bare" (from an Edna St. Vincent Millay sonnet) and "Twas brillig and the slithy toves" (from Lewis Carroll's "Jabberwocky") would garner copyright protection, because of their high degree of creativity and originality, similar to the made-up word "supercalifragilisticexpialidocious" from the 1964 Disney movie "Mary Poppins."

And in the music context, the Sixth Circuit Court of Appeals held in the famous 2005 Bridgeport Music v. Dimension Films case, which involved rap group N.W.A's sample of two seconds from Funkadelic's "Get Off Your Ass and Jam," that the de minimis doctrine doesn't exist in the context of sound recordings -- a decision that sampling proponents have harshly criticized.

Even if "I wish they all could be California girls" is potentially protectable by copyright, that wouldn't be the end of the story. Capitol could assert a fair use defense, arguing that the use of a small portion of the Beach Boys song in what might be plausibly described as a feminist response to it is perfectly allowed under the law.

Universal Music is no stranger to fair use; it asserted that Public Announcement's sampling of a line from George Clinton's "Atomic Dog" in its song "D.O.G. in Me" ("Bow wow wow, yippie yo, yippie yea") was fair use. Alas, a jury disagreed in 2007, as did the Sixth Circuit two years later.