This is an update of a paper entitled “Shareholder Lists, Shareholder Rights Plans and the Oppression Remedy” by Stephen J. Mulhall and Robert J. C. Deane for an Insight Conference in Calgary on Mergers and Acquisitions in Canada, April 6-7, 2000.

Shareholder rights plans, or "poison pills", have been in use in Canada for fifteen years and have become important tools for a corporation faced with an unwelcome take-over bid. Whatever the particular form adopted, the common feature of the various types of poison pills is that they make it prohibitively expensive for a hostile acquirer to gain control of a corporation without the co-operation of the target corporation’s management. The securities commissions and the courts have had to confront these plans and develop principled yet practical approaches. Although the foundations are still being laid, a substantial body of precedent has been developed.

type Securities Litigation and the Oppression Remedy