Paul Tweed, who specializes in bringing U.S.-based celebrities' libel cases to British and Irish courts, told The Associated Press that Lopez, 38, and singer Anthony, 37, were seeking "a six-figure settlement" from the Enquirer, based in Boca Raton, Fla., and its parent company, American Media Inc.
Tweed said the lawsuit would be filed Tuesday in a Belfast court, and in subsequent days in courts in Dublin, London and Paris.
A telephone message left at the National Enquirer wasn't immediately returned Monday. A spokesman for AMI, Richard Balvo, said he had no comment.
"It would be our policy to not comment on it at this time," Balvo said.
The version published March 12 in British and Irish editions alleged the couple were "caught up in a heroin scandal" — and reprinted a 2004 picture of Anthony standing beside photographer Michael Star, who is facing charges of heroin possession and child pornography in the U.S.
The article quoted an alleged friend of Star as saying Star and Anthony were friends.
Tweed told the AP this was untrue and that Anthony didn't know Star even as an acquaintance. Anthony posed for the 2004 photograph, Tweed said, in keeping with his usual hospitality toward backstage concert fans.
There has been a growing trend in international libel suits brought by U.S.-based celebrities in European courts, where libel laws favor the celebrity, not the publication.
"The First Amendment restrictions in U.S. libel law make it virtually impossible for international celebrities or other high-profile individuals to sue successfully," Tweed said. "But with the advance of the Internet, and with U.S. publications now extending their distribution network into Europe, they must subject themselves to libel laws in these jurisdictions."
Tweed said he received approval Monday from Lopez's Los Angeles law firm, Lavely & Singer, to proceed with the lawsuit.
Anthony's spokeswoman declined to comment to The Showbuzz.
It will be Tweed's second lawsuit against the Enquirer. In July 2006, he secured a published apology in the European edition of the Enquirer for an article that claimed pop singer Britney Spears was about to divorce Kevin Federline.
By Shawn Pogatchnik