On Thursday, the Supreme Court of Canada ruled that garbage is exempt from privacy laws. The case involved drug charges, where evidence was taken by police from his garbage. The 7-0 ruling was based on the fact that since anyone could have accessed his garbage, privacy laws did not prevent the police from doing so.
Jewish law is a lot stricter on the rules of ownership then Canadian law. A lost object found on the street does not automatically transfer to the 'finder'. A reasonable amount of effort and a significant waiting time are required in order to attempt to return the object to it's rightful owner. On the flip side someone can declare an object to be owner less making it fair game for whoever passes by.
When somebody puts out their garbage, their intention is for the city to come and take it away. The garbage has no value and there is no intention to recover the contents of the garbage. This makes the garbage free for anyone to take.
The Supreme Court ruling is an extension of basic logic. When someone throws out their garbage it is because they no longer want it. The Supreme Court was correct to quash the argument and concerns from privacy rights groups.