By Gene Cherry

SALVO, North Carolina (Reuters) - Disgraced Olympic and world 400 meters champion LaShawn Merritt may take legal action if USA Track & Field (USATF) does not allow him to compete in this year's world championships, his lawyer said on Friday.

As the reigning world champion, Merritt would normally be an automatic qualifier for the world championships with the U.S. trials determining the other three American 400 meters competitors.

However, a USATF bylaw requires all athletes to compete in the U.S. world championship trials to be considered for the American team.

"Should USATF violate the binding arbitration (in Merritt's doping case) ... and attempt to preclude LaShawn Merritt from competing at the 2011 world championships, the matter would then unfortunately have to be resolved through the legal system," Howard Jacobs, Merritt's lawyer, said in an email to Reuters. The arbitration ruling denies the USATF and other governing bodies the right to exclude Merritt from events after his period of ineligibility expires if the reason for his exclusion would be related to his anti-doping rule violation, Jacobs said.

Since Merritt's participation at Daegu would not affect other U.S. runners, "it is difficult to understand the logic under which USATF would defy the binding arbitration," Jacobs said. USATF officials said earlier on Friday they were considering bending their rules so Merritt could compete. "Our question is, do we want to set ourselves up to create a precedent by allowing him to run," USATF president Stephanie Hightower told Reuters in a telephone interview. "I am a strong believer in rules are rules. But as circumstances and situations change, my philosophy is that you keep an open mind." U.S. DECISION The International Association of Athletics Federations (IAAF) said the issue was entirely up to the USATF to decide. "The 'wild card' IAAF rule clearly states that they (defending champions) are eligible only with the agreement of the national athletics federation," spokesman Nick Davies said in an email to Reuters. "So if the U.S. was to insist on participation (in the American trials), he would not be able to compete in Daegu, even as a wild card," Davies said. Merritt was suspended in 2010 after he tested positive for a banned substance he said was found in a male enhancement product. His participation in the 2012 London Olympics already is under question. An International Olympic Committee (IOC) rule prohibits athletes with doping suspensions of six or more months from competing in the next Olympics. But the U.S. panel of arbitrators who suspended Merritt said the rule could not be used to prevent him from competing in the 2012 U.S. Olympic trials or Olympic Games. The IOC disagrees and the case is expected to make its way to the Court of Arbitration for Sport (CAS) for a final ruling.

"We continue to work behind the scenes in support of a resolution as quickly as possible," U.S. Olympic Committee (USOC) spokesman Patrick Sandusky told Reuters. (Editing by Julian Linden and Peter Rutherford)