Planet Money had a recent podcast titled "The Onion King", where someone took physical control of onion futures, and why that is the one type of future outlawed by congress. http://www.npr.org/sections/money/2015/10/14/448718171/episo...
I was intrigued enough to follow this up, although I didn't listen to the podcast. From wikipedia:
During the hearings, the Commodity Exchange Authority stated that it was the perishable nature of onion which made them vulnerable to price swings. Then-congressman Gerald Ford of Michigan sponsored a bill, known as the Onion Futures Act, which banned futures trading on onions. The bill was unpopular among traders, some of whom argued that onion shortages were not a crucial issue since they were used as a condiment rather than a staple food. The president of the Chicago Mercantile Exchange, E.B. Harris, lobbied hard against the bill. Harris described it as "Burning down the barn to find a suspected rat". The measure was passed, however, and President Dwight D. Eisenhower signed the bill in August 1958. [1]
[1] https://en.wikipedia.org/wiki/Vincent_Kosuga#Regulatory_acti...