[You Need a Thneed]

Originally Posted by Bertuzzied

Don't they blow the play dead when you take a knee and go to the ground? Sure why not? when a QB slides down no one touches him and the whistle goes.

The rules are different for QBs, to protect them from being hit. Even if the rule was possible, the clock would likely still have run out.

Originally Posted by 2009 CFL Rulebook

The ball is dead:
• Whenever a field official blows the whistle
• When an official has signalled a score
• When the ball goes Out of Bounds
• When a forward pass is declared incomplete
• When a kicked ball strikes the opponent’s goal post assembly in flight, without
first touching the ground, a player or an official
• When the ball carrier is tackled and the forward progress has been halted
(tackling is defined as the act of grasping or encircling a ball carrier with hands and
arms)
• When the ball carrier behind the line of scrimmage is firmly in the grasp and
control of a tackler to the extent that the ball cannot be thrown
• When a ball carrier is tackled and driven back towards the ball carrier’s own
Goal Line, an official must assume that an attempt was being made to advance the
ball and that only the actual contact with an opponent prevented such advance.
Therefore, the most forward point of advance shall be considered the point where the
ball became dead
• When the ball carrier is contacted by an opponent and loses balance so that a
portion of the body, other than hands or feet touches the ground, the ball shall be
dead at the point where it was held when touching the ground, or the point where the
ball was held when contacted, whichever is the furthest point of advance
• When the quarterback, in possession of the ball, intentionally kneels on the
ground during the last three minutes of a half
• When the quarterback, in possession of the ball, dives in a feet first sliding
motion, the ball shall be declared dead at the point it was held when another part of
the quarterback’s body, other than hands or feet, touch the ground
• When a player, having possession of the ball in own Goal Area, intentionally
kneels on the ground
• When a ball carrier is on the ground and, in the judgment of the official, is not
attempting to advance the ball, the official shall immediately declare the ball dead.

I don't see anything in there that would suggest a player can just kneel down to immediately stop a play.