Another Spanish town, this one near Salamanca, has picked up on the use of private detectives to track down dog owners who don't pick up. It's a response to complaints about the failure of 'awareness' campaigns.
Detectives will work undercover to spot offending owners and report them to police, who will issue summonses. Other towns have gone the detective route before, with some claiming good results. In Madrid, penalties for not cleaning up can run to big fines or being required to spend a day cleaning.
But none of these measures go as far as the town of Brunete, near Madrid. A few years ago, the town implemented a plan of scooping the poop—and mailing it back to the owners.