From The Horse.com: http://www.thehorse.com/ViewArticle.aspx?ID=11464
European Union to Require Microchipping of Foals
by: Edited Press Release
March 10 2008, Article # 11464
Member states of the European Union have reached an agreement on a new regulation that will revise existing equine identification legislation. The main new requirement is the compulsory microchipping of foals born after July 1, 2009.
The requirement will not be retroactive for older horses and the regulation does allow for member states to approve alternative methods to the microchip.
Microchips provide a link between a horse and its passport and strengthen existing horse identification requirements. Such unique identification of equidae could also prove useful for disease control and surveillance purposes and for the recovery of lost or stolen horses.
In the U.K., the Department of Environment, Food, and Rural Affairs will be consulting with the horse industry over the implementation of the new requirements.