Throughout the history of mankind, clothing has been not only a source of personal adornment and protection, but (unlike most clothing today) an announcement of one's status in society. Often those in power have tried to dictate what people in lower classes might wear. Such laws regarding dress are called sumptuary laws, and were quite common in Medieval and Renaissance Europe. Often nobles were offended when some members of the merchant class, wealthier than their noble "betters," wore fabrics and materials that were more expensive than those worn by the upper classes, and laws were instituted to prevent them from wearing such things.
The wearing of fur was regulated in Tudor England, with only royalty allowed to wear certain furs, and others that could only be worn by privileged people (for example, only those above the rank of a viscount could wear sable and to be able to wear martin (or even velvet) one had to be worth over two hundred marks a year).
In Elizabethan times, the color crimson was only allowed to be worn by royalty (except in underclothing), and the middle-classes were restricted to using velvet only on sleeves.
Sometimes the laws were created to prevent a drain on the economy by the outgoing of gold to foreign countries. In the early 17th century, France outlawed extravagant laces and embroideries on clothing to prevent nobles from sending too much money to the Venetian manufacturers of such products. In fact, Louis XIV finally brought Venetian lacemakers to France and set them up in cities throughout the country, then encouraged the wearing of lace (gold and silver trimmings were still reserved for the exclusive use of the King and his court, however).
Modesty, too, was challenged by fashion, and laws were created to fight trends. In the 14th and 15th centuries, men's tunics and jackets became so short in fashionable circles that it outraged the clergy, who had laws instituted to prevent the hemlines from growing any shorter (but, even so, the hemline eventually reached the waist, and the length of hose subsequently rose from thigh-height to the waist).
More often than not, the laws were hard to enforce and were often violated, as the growing wealth of the merchant classes competed with the nobles.
For further reading, check out these sites:
http://en.wikipedia.org/wiki/Sumptuary_law
http://www.elizabethan-era.org.uk/elizabethan-sumptuary-laws.htm
