Basically compress the crap out of the air, cool the hot compressed air down with outdoor air, separate the condensation from it, then feed it out through the air distribution system, where it magically becomes cold as it expands.
No refrigerant cycle needed.
Works great at 30k, where the outdoor air is very cold all the time.
Not so great on the ground, but still acceptable.
Sucks bawlz when your flight gets delayed, after boarding, and the pilot starts backing off the APU, and shutting stuff down to conserve fuel.
If more government is the answer, then it's a really stupid question.