In my jurisdiction there's a law "Any person who uses of threatens any ... temporal or spiritual injury, or causes or threatens to cause any detriment of any kind, to an elector in order to induce him to vote or refrain from voting... is guilty of a misdomeanor, and is liable to imprisonment for 9 months, or to a fine of $200...'
For a current JW, there's no chance of using such a law - it's privilaged behaviour. But if the elders were watching who was voting at a certain poling place, noting down numbers and then punishing those they saw there including long-since faded JW's, then there just may be a chance.
The judge in Vicki Boyer's case said in common law countries the free exercise provision does not extend to inhibiting the freedoms of non-believers. So, the freedom of ex/non-JW's from criminal behaviour (stalking, assault, threats about voting...) by JW's is (probably) not impinged by the free exercise provision. I suspect that's the case in the US too.