I know companies who have 3 websites with different name and URL. All these 3 websites are ranked in the first and 2nd page of google search results, and they don't let other companies share the first place and have clean competition. So, is it an illegal use to report these sites to google? Thanks
No, it's perfectly legal, this occurs because the company has different websites for different countries - they may not be VERY different but are different enough that google ranks them separately.
The only law in question here is civil, not criminal so nothing is outright illegal.