If you’re in the US, register here: https://registerme.org/
Just stating the obvious. If it’s really religion banning donating organs, not only do they take bodily autonomy from you but also the chance to help save someone else’s life. That would be a shitty religion
The religion bans desecrating corpses, which includes dissection. Donating organs while alive is Ok
The religion can’t “ban” you, they don’t have governmental authority or a police force. The person chooses to participate and chooses not to donate. Unless they live in a particularly authoritarian theocracy it is likely this is a choice.
I disagree entirely with their decision but it’s important to not wildly mischaracterize it as not a decision. They can be an organ donor if they want and live their lives if they choose.