Polyamory

It's a difficult situation to be sure.

Blanket exclusion from romantic relationships and friendships is insane, and that says way more about the existing polycule than the person with HIV.

Sexual relationships are a different topic of course. I think the whole 'we're going to make a blacklist database of people you have slept with' is creepy and abusive. We have readily available STD testing in this part of the world, we have safer sex, and we have agency over ourselves. An HIV-positive person is not a rabid animal to protect your loved ones from, they're a person one can talk to and communicate with.

Of course everyone can set limits about their own sexual activity and even feel uncomfortable with sleeping with someone who has had sexual contact with an HIV-positive person – even if it was with protection – but I think such a bureaucratic process like you described seriously dehumanises the person in question. I generally dislike the tendency of some polycules to become bureaucratised cliques with tribunals, evidence lockers and subterfuge. I don't want to date the equivalent of an HR investigative board.

I think the best way to handle this is to rely on the person with HIV to be responsible about disease management, and set your own boundaries for your own sexual activities in addition. If you can't trust them to responsibly handle their infection status, why would you consider bringing them in the polycule in the first place? And if you can trust them, why the humiliation and dehumanisation of a high court process and privacy-violating 'investigation'?