If they were to ban big .50's, if you have to surrender it or not, the ban would effectively make that rifle useless. Where would you be able to use it? If they don't confiscate, you would not be able to use it at any public facility, and even if you take it out in the bush somewhere, if you are spotted by LE, you would hassled relentlessly. You will have to reload your ammunition.
It would be like if you owned an assault pistol before they banned them. You'll have it, but you cannot give it to your kids, you can't sell it to anyone in state, and you can't use it anywhere.
Very dangerous law! Even if you don't want one, or ever think you will get one, I would fight this law to the end. They are taking your rights one small piece at a time.