Why is the film-maker sentenced to six years in jail?

[9] [10B] The authorities in Iran have sentenced the internationally acclaimed film-maker Jafar Panahi to six years in jail after finding him guilty of crimes against national security. Most of Mr. Panahi’s films, which paint an unflattering picture of Iranian society, have been banned in the country.
    After a period of house arrest in 2009, Jafar Panahi was arrested in March this year and imprisoned. After a huge protest among film-makers around the world, he was released in May with bail set at $200,000. However, the sentence Mr. Panahi has now incurred will put him back in jail and in effect end his career as a director. [10CD] At 51, Mr. Panahi has been told he cannot make films or leave Iran for the next 20 years.