This information was copied from the law web site of
Ladis & Parry at http://www.ladas.com/ipproperty/GrayMarket/GrayMa02.html and http://www.ladas.com/ipproperty/GrayMarket/GrayMa03.html. These are portions taken from the entire article.

The pages are titled:
II. Preventing parallel imports under trademark law and
III. Exceptions to the Exhaustion Rule

There are two prevailing theories regarding exhaustion, namely, that once goods bearing a trademark have been placed into commerce by, or with the consent of, the trademark owner either (a) the owner cannot use his trademark rights to prevent the further distribution of such goods anywhere, the so-called international exhaustion rule; or (b) he cannot use his trademark rights to prevent further distribution of such goods in the same country, but may prevent such distribution in other countries, the so-called national exhaustion rule.

A. The United States approach
(partial)

Thus US laws have long considered that the nature of trademark rights, at least with respect to parallel imports, are universal, namely, once a genuine trademarked product is placed on the global marketplace anywhere in the world, by or with the consent of the trademark owner, the trademark owner may not control the further distribution of that product under a theory of trademark infringement. This theory of parallel imports is said to be the rule of universal, or international, exhaustion.

C. International exhaustion and the Commonwealth
(partial)

As a result, the court decided that proprietorship of a registered trade mark does not entitle the proprietor to control the distribution of his branded goods after they have left his hands. Thus, the Commonwealth position considers that a trademark serves as an indication of the origin or source of the goods, not as a "badge of control" which would allow the trademark owner to control the trademarked goods throughout their passage in commerce.

Other British law countries have interpreted these passages to provide no cause of action to trademark owners against sellers of genuine goods on which a trademark has been placed by the trademark owner or registered user. [15] As Smithers, J. articulated in the Atari/Fairstar case, the trade mark owner who releases goods "on the billowing ocean of trade" will not be able to use the trademark to control the ultimate destination of those goods.

III. Exceptions to the Exhaustion Rule

B. The issues of ownership and consent

Where international or regional exhaustion is the rule, a trademark owner who owns the relevant mark in all of the relevant countries may not prevent the sale of parallel imports, particularly in those jurisdictions that place a premium on the goodwill created in a trademark, since the goodwill is considered to flow to the trademark owner in any case. However, the analysis changes where trademarks in different countries are owned by different parties.