Is it unIslamic to raise female marriageable age above nine years of age?

It's well documented in the Hadiths that Mohammad (PBUH) became engaged to Aisha when she was six, and consumated the marriage when she was nine. Before the Iranian revolution, female marriage was legal at eighteen years of age and above, and this was lowered afterwards to nine years of age to reflect Islamic law as interpreted by Iranian Imams. However, this was then raised to thirteen years of age in 2002 by the Expediency Council. But now recently, Mohammad Ali Asfenani has said Iran has a religious obligation to legally recognise the weddings of girls as young as nine: >"As some people may not comply with our current Islamic legal system, we must regard nine as being the appropriate age for a girl to have reached puberty and qualified to get married," Mr Asfenani, chairman of the parliamentary legal and judiciary committee, told Khabar Online. "To do otherwise would be to contradict and challenge Islamic Sharia law." Is it unIslamic to raise female marriageable age above nine years of age?