If I build my own FM radio and listen to music, I’ve committed no crime.  

If I build a telescope and look at the stars (or the airspace over Area
51, or the nude beach) I’ve committed no crime.  Right?

If I build a radio telescope and capture radio emissions from distant
stars for analysis on my computer screen, I’ve committed no crime.  

So if I take that radio telescope and adjust a few things so I’m
capturing DirecTV transmissions and displaying them on my TV screen, am
I committing a crime?

Here’s my thought: DirecTV’s satellites (I think there are two) are
transmitting radio waves.  Bunches of photons.  If I passively collect
those photons and turn them into something entertaining, how is that
any different– in principle– than listening to FM radio or
stargazing?  It’s all electromagnetic radiation.

Please note this is different than if I bought a DirecTV settop box and
hacked the smart card or whatever… I’m assuming I built the receiver
entirely on my own, and happened to be clever enough to decrypt the
signals.  Is passive recording of electromagnetic waves criminal?

To take it a step further, what if I then started intercepting military
transmissions and broadcasting/selling them?  Criminal or no?

And if the answer to any of these questions is “yes” (or even
“probably”) then who decides what parts of the electromagnetic spectrum
are illegal?  How can the FCC– or whoever– “outlaw” bunches of
photons, or the processing of them?

Strange world.