Yesterday he said: "I feel that the time has come for me to move on and pursue opportunities back in America. My two seasons with the Claymores have been memorable.
"The satisfaction of turning the franchise around and putting it on the right track will stay with me for many years to come."
Keller was instrumental in turning a team that lost eight of their 10 games in the inaugural 1995 season into World Bowl Champions last year.
The World League president, Oliver Luck, paid tribute to Keller, who has served in key positions in three professional American football leagues during his 26-year career.
"Mike has done a very solid job in Scotland," said Luck. "We will miss his leadership and enthusiasm. "The Claymores have consistently improved in each of their three seasons and staged a very successful championship game at Murrayfield last year."Reuse content