* FCA challenges ruling it identified JPMorgan executive
* Supreme Court to examine legal principle of identification
* Ruling has ramifications for FCA enforcement notices
* Judgment could come in three months
By Kirstin Ridley
LONDON, Oct 13 (Reuters) - Britain's markets watchdog and a former JPMorgan executive on Thursday took their legal battle over alleged improper identification to the UK's highest court in a case that could limit details published by the regulator when it fines banks.
In a landmark case, the Financial Services Authority is challenging a lower court decision that it improperly identified Achilles Macris when it fined JPMorgan 138 million pounds ($170 million) over the so-called "London Whale" scandal in 2013.
The hearing in the Supreme Court, which could take three months to publish a judgment, is being closely watched by lawyers as it will set a precedent for seven similar cases in which traders say they were unfairly criticised in FCA penalty notices but were unable to contest findings.
Macris was the former chief investment officer of JPMorgan's synthetic credit portfolio team in London, which ran up $6.2 billion in losses in 2012 in what were called the "London Whale" trades because of their magnitude.
The bank was fined $1.0 billion by U.S. and UK regulators for management failings.
The 55-year-old Greek citizen has so far argued successfully that the FCA's reference in its JPMorgan enforcement notice to "CIO London management" referred to a particular individual and not to a body of people.
Former Deutsche Bank trader Christian Bittar won a similar case last year after arguing that although he had not been named, he had been identified when the FCA fined the bank in a rate rigging investigation in 2015.
The debate hinges in part on how the identification principle should be broadened beyond the use of proper names or unique job titles, as those working in financial services can be more easily identified by peers than ordinary readers.
The FCA's enforcement notices do not name individuals but they often use references such as "Trader A" or "Manager B" when publishing details of electronic messages or emails to illustrate wrongdoing.
Individuals who are identified have a right to respond to the FCA before notices are published, can refer adverse comment to a tribunal and ask the FCA to disclose relevant material.
Some lawyers say the legal debate risks disrupting the regulatory process and limiting the FCA's scope to criticise companies. Others say there are bigger issues at stake.
"The real concern is not third party rights but the regulators' practice of investigating and settling with the institutions before dealing with any individuals caught up in the case," said Harvey Knight, a lawyer at Withers in London.
"Consequently, individuals have to contend with a case that their former employer has already settled with their regulators and the die is cast before these individuals are given any right of reply."
Macris was fined almost 800,000 pounds by the FCA in February for failing to be "open and cooperative" with the regulator as losses mounted in the JPMorgan division he oversaw between March and April 2012.
Macris, who has spent the last four years trying to clear his name, at the time called the fine a "major climbdown" by the FCA.
Bittar, along with five other former traders, faces a criminal trial next September over alleged conspiracy to manipulate Euribor interest rates. ($1 = 0.8042 pounds) (Reporting by Kirstin Ridley; Editing by Keith Weir)