I'm not sure what you mean by Individual Mandate with respect to gun ownership. You mean the second amendment right to own a firearm? The Individual Mandate typically refers to the section of the Affordable Care Act which compels health insurance coverage under a tax penalty.

The Supreme Court has ruled that an individual has the right to own any gun without restriction.

Not quite. You can't own a sawed off shotgun per the Supreme Court. But nonetheless, you're right that personal firearm ownership is a broad right.

I'm with Sam Harris on the subject of gun ownership. It should be incredibly difficult to get a gun license. Think pilot license-level of training, scrutiny, and regulation. But it's such an intractable mess of history and politics right now that I'm not to hopeful for any imminent resolution, even in the next generation. I just want to hear an honest gun advocate come out and say it: mass shootings are the social cost of the ease with which people can buy and own firearms in this country. I resent that that cost is hoisted upon us, but it's not up to me.