Creon has decreed the rebellious Polynices a traitor. As a punishment, he is dishonoring his nephew's corpse by denying it a burial. He is going to let it rot above ground, allowing the birds to eat it. Creon also decrees the death penalty for anyone who tries to bury the body.
Refusing to bury the dead is a deep, deep violation of the moral laws of Greece, which insist on respect for the dead. This puts Antigone into a moral bind. If she obeys her uncle, she is violating her conscience and the will of the gods. She is sinning. However, if she does what is right and buries her brother, she will have violated secular law and will be killed.
Antigone is heroic in her decision to obey the higher moral law and symbolically bury her brother with the proper rituals, even though it costs her her life.
The play's chorus and the words of Haemon and Tiresias show that Antigone is in the right and that Creon is threatening to become a tyrant and bring the wrath of the gods onto Thebes by his refusal to bury Polynices and by passing the death penalty on Antigone.
Antigone is often used as an inspiration by those who defy the immoral laws sometimes passed by governments in order to follow a higher moral code.