The authoritarianism of the Messiah will be turned against corrupt leaders, not the people. And the natural law of God-given rights will still be the law, because it comes from God. And as for guns, the Messiah will greatly enjoy a free people who are completely loaded up with guns, because they are a direct road to a mature, polite and sane society - and they're fun, too. In fact, the only problem with guns is that not enough people have them - something I'm sure the Messiah will correct.
I know that the Messiah of Israel will get rid of all those opposed to his rule, so like you say, that rule will be directed towards those who are good (namely “saved” having accepted him as their personal savior).
But as far as being totally disarmed, yes the world will be totally disarmed and there will be no more weapons ... because there is no need for weapons. All the expense that has gone into that, in the past and present will then (under His rule) be directed towards things that improve society and not things used to protect oneself from evil and assault and other crimes. It will be the first time in human history that mankind could ever be totally disarmed! The Messiah of Israel will be the protection for everyone!
And also during that new world brought to earth by the Messiah, there will be no more carnivores and other animals eaten by those carnivores, as all animals will live peacefully with one another, not killing one another, and even those vicious carnivores and very dangerous animals will play with little children, nothing harming any other thing in creation! And that will include humans not harming any of those living creatures (i.e., “killing” them).
The indications are from the prior explanations in the Bible, also, that at that time, that our meat-eating society will be no more, having gone to vegetarianism. We can’t do that now, but we will be that way when the Messiah of Israel rules.
Many things that we take for granted now, or think “that is my right” will no longer exist. It’s a RADICALLY DIFFERENT SOCIETY!