(Reuters) - Factbox on Olympic 400m champion LaShawn Merritt of the United States, who became eligible to compete in the 2012 London Olympics if he qualifies as a result of the Court of Arbitration for Sport's (CAS) ruling on Thursday against International Olympic Committee (IOC) rule 45.

Age: 25 (Born June 27, 1986)

Place of birth: Portsmouth, Virginia, United States

GOLDEN BOY

Merritt became the world's top-ranked 400 meters runner with his victory over compatriot Jeremy Wariner at the 2008 Beijing Olympics. His margin of victory was the widest since 1896.

He also took gold in the 4x400m relay. Merritt backed up his Beijing performance with another 400m triumph over Wariner at the 2009 Berlin world championships, where he also won 4x400m relay gold.

He returned from a 21-month doping suspension in July and later won a silver medal in the 400m and another 4x400m relay gold at the 2011 Daegu world championships.

An impressive junior athlete, Merritt began his rise to prominence with a 400m silver medal and a 4x400m relay gold medal at the 2007 world championships in Osaka.

FALL FROM GRACE

Merritt failed three doping tests in 2009 and 2010 for a banned substance and was later given a 21-month suspension.

He claimed the positive tests were caused by his use of an over-the-counter male enhancement product that contained dehydroepiandrosterone (DHEA) and pregnenolone.

He accepted a provisional suspension in April 2010.

CHALLENGE TO IOC RULE

In October 2010, an arbitration panel suspended Merritt for 21 months rather than the typical two years and said he could not be prevented from "competing in the 2012 U.S. Olympic Trials, having his name submitted for entry into the Olympic Games or competing in the Olympic Games."

The panel also found "there was (1) no intention to dope, (2) no intention to gain a competitive advantage and (3) no competitive advantage was gained."

It also found International Olympic Committee (IOC) Rule 45 was not in conformity with the mandatory provisions of the World Anti-Doping Agency (WADA) Code. RULE 45

Merritt's arbitration ruling ran contrary to IOC Rule 45, which states that any athlete sanctioned for six months or more will be banned from participation in the next Olympics.

The IOC maintained the rule, adopted in 2008, is not a sanction but an issue of eligibility and that it has the right to put conditions on participation in the Olympics.

Critics of the rule, though, said it created a second penalty for athletes who have served a doping suspension.

In April, the IOC and U.S. Olympic Committee (USOC) asked the Court of Arbitration for Sport (CAS) to determine the validity of the rule.

(Compiled by Gene Cherry in Raleigh, North Carolina; Editing by Martyn Herman; To query or comment on this story email sportsfeedback@thomsonreuters.com)

This story removes reference to Merritt being world champion in first paragraph