Reluctant Volunteer

It was recently told to me that time spent working on my job outside of my work hours (Christmas Break) was considered "volunteering" and not considered lieu time.  I have had a lot of opportunity to think on that comment and I wonder just what kind of message that sends.  What do you (and maybe there is no "you" out there reading me, which I guess will make this a boring question) think of that?  Should we be required to "volunteer" our time to meet the conditions of our job?  Would love to hear some opinions on this one.