FinCEN defines a dealer in precious metals stones and jewels as business that buys and sells more than $50,000 in covered goods. There is an exclusion for retail jewelers who only purchase their supply from other U.S. suppliers. $150,000 in international purchases would make this customer qualify as a dealer in precious metals, stones and jewels.
FinCEN advised dealers of their obligations under the Bank Secrecy Act by publishing an interim final rule in 2005 which describes all of the requirements for a BSA/AML program, OFAC compliance ,etc.
The IRS is responsible for regulating the industry.