See the exceptions below:
USATF 2010 Competition Rules
Rule 163 Section 5
Each competitor must keep in the lanes outside the line or curb marking the inside of the track, including the diversion from the track for the steeplechase water jump. In races run entirely in lanes, each competitor must keep in the allotted lane from start to finish. In races run partially in lanes, each competitor must keep in the allotted lane from the start to the marked cut-in points. Unless a material advantage has been gained, a competitor shall not be disqualified if he or she:
(a) is pushed or forced by another competitor to run out of the lane, or
(b) runs out of the lane on the straightaway, or
(c) runs outside of the outer lane line on the curve.
Excluding the above exceptions, the Referee shall disqualify a competitor if an Umpire reports that the competitor has run out of the lane.
Best,
Christopher