Man of Honour
You have a choice now, and choose to donate. You’ll still have a choice should this be implemented, but would choose differently.
Are you an organ donor for you or for the potential recipient? It sounds a lot like the former, which is fine, but it kind of misses the point about the purpose of organ donation.
I've been an organ donor for ~30 years now for the simple reason that I don't care what's done with my corpse when I'm dead. Because I'll be dead. I have a preference for something useful to be done with it so my wishes are, in order, use anything they can use for spare parts and then use the rest for whatever training or research it can be used for. But I don't care if it's fed to pigs, chucked in the sewers or given to necrophiliacs for a gangbang. Because I'll be dead. Not there any more. Not caring about anything. Just plain not anything.
A choice is about something you do. Something that is done to you isn't a choice. So right now the choice is to donate. The proposal is to take that choice away and replace it with a choice to not donate.