In 397 AD, pants were declared illegal in the city of Rome. The ban was repeated twice, and dire penalties were threatened against anyone depraved enough to wear trousers in public.
This video explains why the Greeks and Romans scorned pants, and surveys the strange and wonderful world of classical clothing along the way.
Suggested Reading
Liza Cleland, Glenys Davies, and Lloyd Llewellyn-Jones (eds.), Greek and Roman Dress from A to Z (New York, 2007)
Alexandra Croom, Roman Clothing and Fashion (Stroud, 2010)
Mary G. Houston, Ancient Greek, Roman, & Byzantine Costume and Decoration (London, 1947)