"Draft card" was a colloqial term for the
card issued as proof of
registration for "the
draft," military
conscripttion, in the
U.S., during the times when the U.S.
Congress had authorized drafting
soldiers. The U.S. government never used the term officially, and in fact the
Selective Service web site notes that before the early
1970s, there were two cards, a proof of registration and a
classification card, that were issued to the men who registered. Regulations required that registered men have the former in their possession at all times until draft registration was suspended in
1974; this rule was not reinstated in
1980 when draft registration started up again. (Some people still refer to the proof of registration issued now as a "draft card.")
Draft cards were issued in the past -- many genealogy sites have information on interpreting the cards filled out for World War I draft registration in the U.S. But they are most famous for their role in protests against the Vietnam War; David Paul O'Brien burned his and was arrested and prosecuted for it. His case was argued before the U.S. Supreme Court, and it was ruled that arresting him for burning his draft card did not violate his right to free speech, because he had many ways that he could speak out against the war without destroying a then-integral part of the Selective Service registration system. Many other card burnings took place, despite the fact that trying to evade the draft, if found out, put one in a category of "delinquents" who were the first to be called on to go into military service.
Source:
http://www.sss.gov/FSdraftcd.htm
http://www.ancestry.com/search/rectype/inddbs/3172.htm
http://wings.buffalo.edu/courses/sp01/ugc/112d/example_topics.htm
http://www.ustrek.org/odyssey/semester2/040401/040401nickdraft.html