He began playing in local events organized by Chess 'N Math, and had a candidate master rating by age 11.

[3] Le Siège, at 16, won the 1992 Canadian Chess Championship at Kingston, Ontario, defeating Kevin Spraggett in the key game.

[4] Awarded the International Master title, Le Siège qualified for the 1993 Interzonal Tournament at Biel, Switzerland.

[6] He won the Canadian title again in 1999 at Brantford and in 2001 at Montreal after winning a tie-break playoff against Spraggett.

[11][12][13] Le Siège virtually retired from competitive chess from 2004 to 2015, when he resumed by defeating Evgeny Bareev in a rapid match 1.5-0.5.