According to the Third Geneva Convention itself (the one covering POWs), for a person to qualify as a POW and be accorded the treatment proscribed in said convention, that person must be affiliated (either regular army or militia meaning some sort of uniform) with a "High Contracting Power" (a state that was party to the convention but for argument's sake we'll say any state).

CENTERFORSECURITYPOLICY: Amnesty ignorant again

This will abolish the current practice whereby employees get a National Insurance (NI) rebate of 3.4% for contracting out of the second state pension to enter final-salary schemes, which affect more workers in the public sector such as in the NHS, the UK's largest employer.

BBC: Finance

The Department for Work and Pensions confirmed that under a single-tier pension there would be no contracting out so workers would pay more national insurance, but as a result they would get a better state pension.

BBC: Flat-rate pensions plan revealed