There are many different drone regulations but sometimes there are areas that are not so clear which is why there are FAA drone legal opinions. The FAA is the authority on the Federal Aviation Regulations. A person can request the FAA Office of General Counsel to write a letter of interpretation on a particular issue. The FAA then responds with a letter of interpretation which is helpful in understanding the FAA’s legal view on things.
While these opinions are NOT the law, they are a window into the mind of the FAA to see how they interpret certain things. If you want to try and stay out of the FAA’s crosshairs regarding an enforcement action, you can read through these to get an idea of what the FAA thinks.
Keep in mind that if they tried to prosecute you for a violation of their interpretation, not the law, a judge may not agree with their interpretation. In short, these interpretations are really just FAA opinions, not the law. But these interpretations are also not checks to pay for your attorney to defend you. ;)