I'll bite. They don't, but they very much do have jurisdiction over the operation of domestic corporations engaged in interstate commerce, which this clearly is.
Is what Swarm did bad? Yes, if we were to take FCC at face value (why should we?). Should the FCC be allowed to reprimand this american company? Probably, assuming FCC is telling the truth. Should the FCC act like the universal arbiter of space? No, it should not, and the sociopolitical attitude displayed here is much worse and harmful than the space pollution from Swarm.
And I disagree with the "sociopolitical attitude being bad". I fully believe that this "endanger other's things and don't care about it" attitude given by Swarm is the more dangerous one.