Here I'll save you the trouble. Here is the actual US code in regards to hobbyist flight. First we have the Small UAS Rule (Part 107), however part 107 doesn't apply to hobbyists. Part 107 does not apply to UAS flown strictly for fun (hobby or recreational purposes) as long as these unmanned aircraft are flown in accordance with the Special Rule for Model Aircraft (Section 336 of P.L. 112-95). So let's go to the special rule for model aircraft.
https://www.faa.gov/uas/media/Sec_331_336_UAS.pdf
Section 336 states:
SEC. 336. SPECIAL RULE FOR MODEL AIRCRAFT. (a) IN GENERAL.—Notwithstanding any other provision of law relating to the incorporation of unmanned aircraft systems into Federal Aviation Administration plans and policies, including this subtitle, the Administrator of the Federal Aviation Administration may not promulgate any rule or regulation regarding a model aircraft, or an aircraft being developed as a model aircraft, if— (1)
the aircraft is flown strictly for hobby or recreational use; (2)
the aircraft is operated in accordance with a communitybased set of safety guidelines and within the programming of a nationwide community-based organization; (3) the aircraft is limited to not more than 55 pounds unless otherwise certified through a design, construction, inspection, flight test, and operational safety program administered by a community-based organization; (4) the aircraft is operated in a manner that does not interfere with and gives way to any manned aircraft; and (5) when flown within 5 miles of an airport, the operator of the aircraft provides the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport) with prior notice of the operation (model aircraft operators flying from a permanent location within 5 miles of an airport should establish a mutually-agreed upon operating procedure with the airport operator and the airport air traffic control tower (when an air traffic facility is located at the airport))
And that number 2 there is the gray area. The FAA does not define what a "nationwide community based organization" is. The AMA is an example of one, but it is not the only one. Since the FAA has no rule or definition of this, the term can be applied extremely broadly. One could join such an organization that does not require LOS. And in regards to the 400 feet AGL, even the AMA doesn't require that.
Your questions answered-The 400 foot limit for model aircraft. | AMA Government Relations Blog
Academy of Model Aeronautics - FAA UAS Frequently Asked Questions
Q: Am I permitted to fly above 400 feet? What if I had to check a box saying otherwise on the federal registration website?
A: Yes. AMA members who abide by the AMA Safety Code, which permits flights above 400 feet under appropriate circumstances, and are protected by the Special Rule for Model Aircraft under the 2012 FAA Modernization and Reform Act.
At the end of the day, the wording on the FAA website has done a great job convincing people that these are laws, when they are not.