14 CFR § 101.23

You must operate an amateur rocket in such a manner that it:

Is launched on a suborbital trajectory;

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;

Is unmanned; and

Does not create a hazard to persons, property, or other aircraft.

The FAA may specify additional operating limitations necessary to ensure that air traffic is not adversely affected, and public safety is not jeopardized.