b'A red flag law, in general, is when someone can go to the authorities and "out" someone as a potential danger to society. Law enforcement and the courts would then intervene to preemptively determine if a crime has been committed &/or temporarily remove firearms. Due process, or fair treatment through the normal judicial system, would be determined in the final legislation. It could very easily turn into a slippery slope.
https://justthenews.com/government/congress/federal-red-flag-gun-bill
https://www.merriam-webster.com/dictionary/red%20flag%20law'