Outside of the Military, there are two distinct "work" environments - firstly, your job/career and secondly, things you might decide to do voluntarily because they are fun or life-enriching.
The former is a contracted agreement whereby you are compensated for your labour and any changes to that contract are subject to negotiation between both parties.
The latter is an acceptance by you that for your fun, interest or enjoyment, you may have to cough-up a bit of your own cash but it's worth it.
I would hope that our military are firmly in the former group and any attempt to "squeeze" them by changing their circumstances arbitarilly, is seen to be unfair at best or indeed illegal.