Re: not subect
Also, FAA might not like it, but below a minimum flight level, you are NOT subject to FAA rules
That depends on where you are in any country.
In the UK class G airspace starts at 400 ft AGL, which is also the maximum permitted height for UAS, i.e. RC models and drones, operation. However, a UAS cannot be flown within an ATZ (a circle of normally 2 nautical miles radius from the midpoint of the runway of a licensed airfield) or in Control Zones, such as the London CTR. Both ATZ and CTR airspace starts at ground level. CTR airspace is typically class A - D airspace as well, which means no entry except when you're following directions from ground control.
So, no you CAN'T fly a drone in Hyde Park or on Clapham Common because both are inside the London CTR. You can, however, fly a control-line model if the landowner allows it because these models are tethered to the pilot by the lines used to control the model.
In the USA things differ in detail, but the general rules are the same. I just dug out my copy of the FAA regulations from 2001. FARs part 71 defines the airspace classes and what can be done inside each of them. Only classes E and G have a lower limit - 1500 ft AGL for class E and 1200 ft AGLfor class G airspace. Since that is the bottom limit for aircraft ops, it would appear, unless the FARs have changed since 2001, that you can legally operate a drone or RC model up to 1200 ft in class G, up to 1500 ft in class E and not at all in class A,B,C or D airspace in the USA.
Disclaimer: the FARs are written in an obtuse, legalistic fashion where later statements can and do amend or override earlier statements. They are hard to understand because of this. This means that I could have easily have misinterpreted them. They also jabber on: the FARs applicable to glider pilots occupy 101 pages of A4 paper, while the much more readable UK "Laws and Rules for Glider Pilots" fit comfortably onto 69 pages of A5 paper.