Censorship
There is much debate about when censorship should be allowed.  For example, U.S. President Richard Nixon censored the New York Times when they tried to publish articles about the Pentagon Papers, a group of classified military documents that showed that Nixon and the military lied about the Vietnam War.  The Supreme Court in New York Times Co v. United States overturned the censorship, saying that Nixon had not shown it would be dangerous to the military, just embarrassing.  In other countries, journalists and bloggers (who are usually not seen as journalists) are sometimes arrested for saying bad things about the government.  In Egypt, Kareem Amer was famously arrested for insulting Islam and calling the president of Egypt, Hosni Mubarak, a dictator.