I am aware of one person who has two dogs, one smallish and one hugeish ( certainly big enough to pull a grown man over ). This person used to let both dogs off the lead on the beaches and campo. However, after the large dog had a couple of altercations with humans , ie knocked one guy off his bike on the campo and killed a neighbours pet cat this person still refused to keep the dogs on their leads. She was visited by the Civil Guardia and asked to keep them on leads. She ignored their request.
It was only after the large dog took a chunk out of a guy's calf while he was running ( on Macenas beach as it happens ) did matters change. The Civil Guardia visited once more. the person was told in no uncertain terms that they were to be on leads and wear muzzles when outside of their residence. The person was told if there was any further trouble the animals would be seized and put down.
I have been a dog owner in my time and I too rarely ever needed to use a lead and certainly not a muzzle but it does seem that in the locale people do have a worry about dogs in general on beaches and campo. Its unfortunate that the minority spoil it for the majority of well behaved animals. But fear, unfounded or not, is fear. And so that impacts on everyone.