The following is reprinted from http://www.news.ontario.ca/ene/en/2009/12/reducing-greenhouse-gas-emissions.html:

Ontario is closer to establishing a cap-and-trade system to reduce greenhouse gas (GHG) emissions.
Today, the legislature passed the Environmental Protection Amendment Act (Greenhouse Gas Emissions Trading), the foundation for Ontario's cap-and-trade program.  

The act allows Ontario's program to link to other systems in North America and abroad. Aligned systems would maximize trading opportunities for industry, helping them to make GHG reductions at lowest cost.  
 
A cap-and-trade system uses market forces to help industry reduce GHG emissions.  It is an effective way to reduce the threat of climate change caused by carbon emissions. Cap and trade is also expected to boost the production of low-carbon processes and green technology, creating new jobs and business opportunities.

This legislation is the latest leadership measure taken by the Ontario government in its broader action plan to tackle the threat of climate change and achieve real GHG reductions that will protect and improve the environment.