From the CFL website
Instant Replay is a system designed to assist Officials in evaluating play situations on the field where judgment may be in question due to:
* their positioning and limited view of the action;
* the speed of the action, which makes a split second decision difficult;
* an error in judgment.
All Instant Replay Reviews will be operated on a Challenge system for 2006, except for the last 3 minutes of the second half and in overtime.
The system operates with the "Replay Technician" and the “Replay Official? recording the television video feed onto a VTR machine located in the League Supervisor booth at the press box level in each stadium. This recorded tape will be used for Instant Replay Review.
To initiate an Instant Replay Review, the "Head Coach" will execute the challenge prior to the legal snap of the ball on the next play, by stepping on the field, getting the attention of the nearest official, and throwing a marker.
Each team will have the ability to execute 2 challenges per game prior to the last 3 minutes of the second half.
The first challenge will have no impact on team time outs, regardless of the outcome of the challenge.
A second challenge, if unsuccessful, will result in the loss of a team time out,either first or second half.
If a team has used their team time out in the first half, and their second challenge occurs in the first half and is unsuccessful, then the team will forfeit their second half team time out.
In order to execute the second challenge in the second half, a team must have a team time out remaining.
If both first half and second half team time outs have been used prior to any challenges, a team would continue to have the opportunity for one challenge.
In the last 3 minutes of the second half, and in overtime, all Instant Replay Reviews will be initiated by the Replay Official in the League Supervisor’s booth.
All Instant Replay Reviews will be conducted by the Referee at field level, on a field level monitor.
An officiating decision made on the field will be reversed only when the Referee has indisputable visual evidence that the call should be changed.
Once an official has whistled a play dead, Team B (the defence) cannot gain possession of the ball, unless otherwise specified in this manual.
The Referee will have sole responsibility in evaluating team challenges and deciding, based on this manual, whether or not a play is reviewable.