Sir Michael Lyons said the changes would provide "much-needed clarity"
The BBC Trust is to limit further mergers and acquisitions by BBC Worldwide, following a review of the corporation's commercial activity.
Deals such as buying a 75% stake in Lonely Planet travel guides in 2007 will no longer be allowed unless there are "exceptional circumstances".
The report said the "scale and nature of the Lonely Planet acquisition" would not be considered again.
The BBC Trust has also ruled that Lonely Planet would not be sold off.
BBC Worldwide is the corporation's commercial arm. The Trust said it wants to ensure that Worldwide's plans secure the "best value for licence-fee payers".
The chairman of the Trust, Sir Michael Lyons, said: "Worldwide is a successful business which brings both significant financial benefits for the licence fee payer and a tangible boost to the creative economy.
"But the trust and the executive both acknowledge that the boundaries for Worldwide activity need to be clearer."
He added that he thought the changes would "provide much-needed clarity and a greater alignment with the BBC's public purposes, without stifling Worldwide's ability to perform as a thriving and profitable entity".