This is settled in international humanitarian law. Per Human Rights Watch, citing ICRC guidance: "reservists of national armed forces are considered civilians except when they go on duty." [1] Off-duty at a music festival unambiguously qualifies as not on duty.

The argument that prior military service permanently strips civilian status has no basis in IHL. If it did, every Israeli who'd ever served (which is nearly all of them, given conscription) would be a legitimate target forever.

So: not a targeting framework, more like a justification for killing the entire population.

On your second point: Israel's targeting decisions are also subject to IHL, and where they kill civilians unlawfully that's also a war crime. That's not a defence of Hamas... it's the same standard applied consistently.

"They do it too" doesn't make either lawful.

For what it's worth, joining Hamas is a choice; IDF service is compulsory. The cases aren't analogous.

[1] https://www.hrw.org/news/2023/10/09/questions-and-answers-oc...