Part of the Right to Vote is chosing not to Vote.
Especially when there is no morally acceptable choice to make.
For it to be a Mortal Sin to not vote it would have to meet the same criteria that all Mortal Sins have to meet.
1857 For a sin to be mortal, three conditions must together be met: “Mortal sin is sin whose object is grave matter and which is also committed with full knowledge and deliberate consent.”
So chosing not to vote would meet at least the third condition and I can see how it would meet the second but can anyone show us how voting is a objce of grave matter.
Then there are also these form the Catechism that state what a sin is.
1849 Sin is an offense against reason, truth, and right conscience; it is failure in genuine love for God and neighbor caused by a perverse attachment to certain goods. It wounds the nature of man and injures human solidarity. It has been defined as “an utterance, a deed, or a desire contrary to the eternal law.”
1850 Sin is an offense against God: “Against you, you alone, have I sinned, and done that which is evil in your sight.” Sin sets itself against God’s love for us and turns our hearts away from it. Like the first sin, it is disobedience, a revolt against God through the will to become “like gods,” knowing and determining good and evil. Sin is thus “love of oneself even to contempt of God.” In this proud self- exaltation, sin is diametrically opposed to the obedience of Jesus, which achieves our salvation.
I just do not see how not voting fits into these definitons.
And then let us not forget, if not voting is a sin, or even a mortal sin, then all those people who live in countries where they do not get to vote are commiting sins becuase they are not voting.