Italian mobs selling "virgin olive oil" likes that article.
My main point is that I am not able to tell real virgin olive oil from scam one. From what I understand most of "virgin olive oil" on supermarket shelves is scam.
Try finding bottles that explicitly list the acidity of the oil. The good stuff is really low. Extra virgin is considered .8% or less. I would shoot for something that explicitly lists 0.3% or better.
Adulteration of olive oil typically happens in transit/shipping by wholesalers, not by producers. Spanish or Italian olive farms aren't diluting with corn oil or whatever during production on the farm/when pressing, it's by aggregators who are buying and selling oil in bulk by volume. So if you're buying olive made, processed, and bottled by a single farm whose origin is local you're structurally at less risk than a generic "Italian" oil or one that says the country of origin could one of 3-4 countries. Also California has a mandatory sampling and testing program https://www.oliveoilcommission.org/
Primarily because there are stricter requirements via FDA on the US food supply. If a US producer gets caught adulterating they're going to face legal issues that a foreign producer will not face. Not saying it's not possible that CA producers could be adulterating, but if they get caught there will be consequences that an importer won't face - the importer can just say they were trusting their suppliers overseas.
Also found this (from 2010): "The research team found that 69 percent of the imported oils sampled, compared with just 10 percent of the California-produced oils sampled, failed to meet internationally accepted standards for extra virgin olive oil." https://www.ucdavis.edu/news/most-imported-olive-oils-don%E2...