Can it? I know that it's been done, historically. I'm not sure that sort of private property confiscation will ever happen again. Sure, anything is possible since there seem to be an infinite number of loopholes in the Constitution - it's pretty much a useless document when Uncle Sam wants it to be.
The main issue with gold is even if not confiscated, you'd need to figure out a way to divide it for transport and spending, as well as not getting caught during the latter. It's a good store of value, but that's about it.