That's not correct. Section 336 said that the FAA could not promulgate any new rules. It did not specifically mention registration and included the caveat that it did not prevent the FAA from enforcing airspace safety - those were not separate powers:
We are arguing the same thing... I say Section 336 specifically did not allow for the registration. You say that Section 336 allowed it, outside of 336, under their safety authority.
You can assert your opinion that registration did nothing for safety, and I tend to agree, but you cannot cite it as a fact, and the motives that recreational fliers had for registering are not relevant to the law. Registration was struck down because, however one looked at it, it clearly was a new rule.
I can cite it as a fact as the registration was never used in that capacity. The database was _never_ used to trace a drone to the owner. The FAA stood in front of the public and said that the issue was not obtaining the drone, it was matching the drone to the user. That was a lie and the database was _never_ used in that function.
You can only argue a 400' limit as a safety issue as much as you can argue for 350', 250', 200' etc. limit to the same degree. When you registered you did legally agree to fly under 400':An altitude limit, such as 400 ft, is relatively easy to argue as an effective safety provision, but the FAA did not attempt to make it a rule (336 prohibited that too) and instead simply tried to get hobbyist agreement not to exceed it as part of the registration process.
"To operate as a hobbyist, you must operate according to the safety guidance you have acknowledged and in accordance with a community based set of safety guidance. For further information on the safety guidance visit"
"Please remember the Safety Guidance:
- I will fly below 400 feet"