Bummer. This really NEEDS to be an option. Having the game remove your options is not fun.
People in this thread keep stating they can't see how this should/could work in gameplay terms.
It's precisely for gameplay terms that it should be in. Not for all proposals, but there is one type in particular that needs this mechanic: Nuclear Weapons.
One of the proposals was a Nuclear Non-proliferation Treaty. I should be able to not sign the treaty if the vote passes (with the consequences being harsh, like auto-trade embargoes or justification for another civ to declare war, etc.) Further I should be able to be duplicitous to the world... sign the treaty but continue to make nuclear weapons (or worse use them
) Or similarly: Trade embargoes... I should be able to break a supported trade embargo... much to the chagrin of my allies.
In this way you are not restricting options from the player, you're providing more risks and rewards to weigh and make decisions with. I will not like a forced on mechanic... e.g. the world has voted that they don't like the Rifleman unit; therefore no one can built it anymore.