Just an outside-the-box thought, tossed out there for discussion:
Why seize the gold early in the crisis, when you can get plenty of folks to turn it over voluntarily?
First, you ban further private purchases/sales of gold "only for the duration of the present emergency." Next, you set the conversion rate of "old dollars" to "new dollars" such that people converting cash take a significant haircut in total purchasing power (bank accounts, 401(k) accounts, IRAs and the like take an even-greater haircut), while folks who sell their gold to the government will take a smaller haircut, based on the pre-EMP price of gold. Add to this by announcing at the outset that the gold haircut will increase significantly after a fairly short period of time, and many people will see plenty of incentive to cash in their gold, all the while laughing at those fools who didn't have their money protected by having gold on hand.
Finally, debt conversions from old to new dollars slam creditors with a haircut even deeper than those imposed on bank accounts, 401(k) accounts, IRAs and the like.
Add all these together, and you have a massive transfer of wealth from the makers to the takers, all based on manipulating the degree of losses sustained in the conversion of old dollars to new.