If so does anyone know which laws are causing the restriction?
I think it has to do with taxes, I found on Google there is for example a 28%
capital gain tax on gold in the USA.
Forbes explains why gold and silver coins are not used to pay:
There are a number of reasons, but lets focus on one: the capital gains tax. The Fed debases the dollar, but of course not gold and silver. As the dollar falls, the prices of the metals rise. The government treats this as a gain and upon sale of the metal, levies a tax on it. If the dollar loses half its value, then the gold price will double, say from $1,400 to $2,800. The government takes 28 percent of this difference, or about $400. The only way to avoid this tax is by not selling. Thus gold and silver are best suited to long-term preservation of wealth: hoarding.