I think they pumped the "priviledge not a right" mantra into us in boot camp to groom us for mindless obedience. However, being a human being that can use his mind, I still believe that liberty is definitely only a priviledge granted by the command, distinctly different than the RIGHT of leave. And yes, it can be revoked by anyone in that chain. My small section (15 Marines) once had to work 3 weeks straight, with an alternating 2-guys-get-12 hrs off every 4 days, simply because the mission had to be accomplished, and we were "short personnel." That defficiency and remedy for it were determined by a SSgt, who was challenged up the chain by several LCpls who had plans that were obviously curtailed, but the CO ended up backing him completely and without compromise (though who knows what he had to answer for behind closed doors). All of us were "compensated" later with an extra day tacked onto a weekend, making it a "free" 72, but it was made clear that this was only due to the generosity of the command, so to speak.
Bottom line I learned: liberty is definitely only a priviledge - granted usually by default yes - but a priviledge just the same. The SSgt's order to cank liberty was lawful.
WHICH brings up another detail of interest! Something they stressed in Sgt's course a few yrs ago was the difference between a lawful and a direct order. We enlisted types are restricted to lawful ones - those already provided for by previously established laws, regulations, or procedures. But correct me if I'm wrong, you hossifers can give a direct order, meaning YOU are the sole determinant at the time that the order is given under proper grounds (i.e. PVt -go jump off that cliff) and without question, a subordinate must obey. Granted you'll have to put your commission on the table if you were totally out of line, but your training and your 4-yr degree says that the government can trust you to make seemingly out-of-the-box decisions that directly affect others' lives.
I saw that in OIF where (I can't detail) but we all assumed a Capt was out of his mind when he had us do something; but we did it, and it turned out to have quite probably saved our lives.
Edit: And didn't seem "lawful" at the time, was my point...