I could be wrong, but I know of no restriction or requirement like you mention.
http://www.sec.gov/investor/pubs/ininvest.htm
Stocks Trading on Foreign Markets
If you want to buy or sell stock in a company that only trades on a foreign stock market, your broker may be able to process your order for you. These foreign companies do not file reports with the SEC, however, so you will need to do additional research to get the information you need to make an investment decision. Always make sure any broker you deal with is registered with the SEC. It is against the law for unregistered foreign brokers to call you and solicit your investment.
U.S. residents won't be able to trade almost any futures or options on foreign exchanges, due to U.S. regulations. A few futures products are "whitelisted" by some U.S. bureaucrats (CFTC I think, or perhaps SEC). Foreign exchanges that want their products whitelisted for U.S. residents have to pay money and dance to the tune of the U.S. government (CFTC?). There is a U.S. government organization that does nothing else but control and update this list day in day out year in year out, write garbage (excuse me) publications and opinion letters etc.
I looked at that garbage (excuse me) list and it seems arbitrary. For example Euro Stoxx 50 options, the equivalent of SPX options in Europe, are prohibited for U.S. residents.
As a result, U.S. citizens can't do many things, like writing covered calls on foreign equities or indexes, hedge their international portfolios with foreign index futures, etc.
I can't believe that this kind of government overreach is possible in a supposedly free country like the U.S. I believe investors know better what's good for them than some government organization. Additionally, it is an arbitrary discrimination of individuals and small investors vs. organizations. You can only get an exemption if you have > $100M.
This seems to be some antiquated law from decades if not close to a century ago, the sole purpose of which in my humble opinion is to justify the job positions and the existence of the agency that controls that "white list" and extracts money from foreign exchanges. Foreign futures and options are not any more or less risky than U.S. futures and options; and even if they were, let U.S. citizens do their research and make that determination what they do with their own money, not the government.
I found no way to circumvent or bypass this crap with U.S. brokers.