The Canadian Anti Spam legislation exposes folks to stiff penalties for sending commercial messaging to people who have not explicitly. Here is a great webcast that talks about CASL ( ). 

It is a best practice to only send emails to those people who have explicitly given permission. This is done with ActiveDEMAND by using the 'Opt-in' survey field in your forms. 

All contacts who check this field when submitting a form have their explicitly permission logged with a timestamp. This permission can be revoked at any time by a client via an unsubscribe (again logged). In your campaigns there is a checkbox that, if checked, will only send emails to those folks that have an opt in status set to true.

So, in short, use the Opt In survey field. Check the option to only send to those folks that have opted in. This will reduce any exposure to CASL fines significantly.