NEW YORK • There is a major beef going down between married couple Kim Kardashian and Kanye West and pop star Taylor Swift.

But the latest twist may have put West on the wrong side of the law - and Swift has already threatened him with criminal prosecution, according to TMZ.

It all started with a public relations battle over a lyric in the song Famous from West's latest album The Life Of Pablo: "I feel like me and Taylor might still have sex... Why? I made that b***h famous."

Swift's team denied she signed off on the lyrics and the singer made what some have said may have been a thinly veiled dig at West while accepting a Grammy in February.

Kardashian basically accused Swift of lying about her knowledge of the song's lyrics in a recent GQ cover story - and on Sunday night she released footage on Snapchat that appears to show a phone call between Swift and West in which he talks about the first half of the lyrics as proof that the songstress approved it before it was released.

In the footage, Swift, 26, gave her approval - at least in part - to the song.

She told West, 39, of the lyrics, "I really appreciate you telling me about it. That's really nice. It's all very tongue-in-cheek either way."

"If people ask me about it, I think it would be great for me to be like, 'Look, he called me and told me about the line,'" Swift says in the call, which took place before the February release of Famous.

Not long after, she released a statement on Instagram stating she had not approved of the song and that West had not delivered on a promise to play her the final version before its release.

"Where is the video of Kanye telling me that he was going to call me 'that b***h' in his song? It doesn't exist because it never happened... While I wanted to be supportive of Kanye on the phone call, you cannot 'approve' a song you haven't heard," she wrote.

"Being falsely painted as a liar when I was never given the full story or played any part of the song is character assassination."

Making that recording may have violated state wiretap laws.

"Generally, what matters is the location of the person recording the call," said Mr Marc Rotenberg, executive director of the Electronic Privacy Information Center.

California, where the Kardashian- West clan lives and, TMZ reports, from where West called, is one of a handful of states that goes further than the federal wiretapping standard, which requires only one half of the conversation to approve of a recording.

Instead, the state requires everyone on a call to consent to a conversation being recorded, Mr Rotenberg said.

West's press team did not immediately respond to a request for comment. In her Instagram statement, Swift said the call was "secretly" recorded.

If Swift was really unaware of the recording, as her post suggests, and if West indeed called from California, then he could be in violation of the California law and potentially face a fine of up to US$2,500 (S$3,380) and up to a year in jail, according to the penal code.

According to TMZ, Swift's lawyer sent West a letter threatening him with the law in February after hearing about the recording and demanding he "immediately destroy" it and assure Swift that the recording had not already been shared.

In Kardashian's GQ interview, she also said Swift's lawyers had sent a letter demanding that the footage be destroyed. Washington Post also reached out to Swift's press contact to confirm that she was unaware the call was being recorded.

However, one snag in the California statute might get West off the hook. The law applies only when "one of the parties has an objectively reasonable expectation that no one is listening in or overhearing the conversation", according to Harvard's Digital Media Law Project.

Given that West appears on his wife's reality show - and Kardashian's career is based on her most intimate moments being taped - his legal team may argue that no one could reasonably assume conversations with the pair were private.

WASHINGTON POST