How do they know you have gold in your possession and can they make you turn your gold in? It might be a lot harder to sell without some sort of confiscation, but they aren’t going to go on gold raids. Gun raids on the other hand I could see.
Securities and exchange commission records. If you buy it on the commodities exchange, there is a record. If you buy it from a gold dealer, there is a record. If you later sell it or trade it and you don't keep a record, the IRS will assume you still own it. They'll tax you every year until you show them where you sold it and to whom.
In the Great Depression I believe they seized everyone’s safety deposit boxes (for the good of the country, not the cheeldren). Lesson there is...if you own gold, don’t store it where the fed gov can get it’s grimy paws on it ....like in a bank, especially if that bank has been compromised (pwned) by Uncle Sam, aka Unk Obammie.
Like the ACORN ho said, bury it in a tin in your back yard. It’d be safer.