Since when is it legal for the cops to go through your trash that is on your property?
Since pretty much forever. The rationale seems to be that once you have put something in the trash, you have relinquished possession, and then anyone else is free to use it for any purpose.
Although I should add that if the trash is still on your property (within your curtilage), most jurisdictions will still require a warrant. If you have put it out on the street, probably not.
any damn time they want to. DEA probably. Not cops.
Also trash is usually located on city property.