14 CFR §101.23

1. (a)You must operate an amateur rocket in such a manner that it:
   1. (1)Is launched on a suborbital trajectory;
   2. (2)When launched, must not cross into the territory of a foreign country unless an agreement is in place between the United States and the country of concern;
   3. (3)Is unmanned; and
   4. (4)Does not create a hazard to persons, property, or other aircraft.
2. (b)The FAA may specify additional operating limitations necessary to ensure that air traffic is not adversely affected, and public safety is not jeopardized.