The FAA has authority over all aircraft operaions (including models) regardless of what and where you are flying. The problem is in the fact that there are some issues with how people interpret the wording. Class G (often called uncontrolled) airspace does not mean they have no authority, only that specific rules apply. Basic rules of flight always apply making it by definition still "controlled" by the FAA. Navigable airspace is airspace that the FAA has control over what the public can do, such as if you wan't to build a tower and it will extend into navigable airspace you would then have to get permission to build. If it doesn't extend into navigable airspace then no permission is needed. Again the FAA still has control over aircraft operations even in non-navigable airspace, hence the reason for last line of Littlecrankshaf"s quote.