Other participants in the bidding process withdrew their bids, saying that CN had unfair access to confidential information about their own operations, provided by the government, and at least one bidder (Canadian Pacific) privately stated in since-released communications that the bid was "rigged".

Informed consent is not a contract, and the participant may withdraw from the trial at any time.

In clinical trials, participants may withdraw from the study, for example, due to adverse effects.

Another initial participant in the review, Berlin Cameron/Red Cell in New York - part of the Red Cell division of the WPP Group - withdrew from consideration.

What's more, these easily understandable defined contribution plans can be established in a form that permits participants to borrow from their accounts or withdraw money in case of financial hardship.

G.E. has an employee savings plan that lets participants withdraw money after three years.

One participant, the Leo Burnett Company unit of Leo Group in Chicago, withdrew because of a potential conflict.

In March, one participant withdrew: the Chicago office of FCB Worldwide, part of True North.

But the obligation has to be balanced with a cardinal rule of human experimentation - that a participant can withdraw from a trial at any time no matter how awkward it may be for the patient or the doctor.

Informed consent is not an immutable contract, as the participant can withdraw at any time without penalty.