These dogs are generally not just out for walks.And if they are in public space, I will assume this follows law.
I will have to re-read this news article, but the actual release by the DOJ doesn't mention anything about phoning ahead.
Not sure where they are getting that from. Where would the dog smell the weed? Did they stick him out the window on the highway?
https://mobile.twitter.com/AdamSchefter/status/1230310952001843201?ref_src=twsrc^tfw|twcamp^tweetembed&ref_url=https%3A%2F%2Fd-10062135951848900006.ampproject.net%2F2002200031230%2Fframe.html