In light of David Hicks' sentencing to nine months in an Australian prison, John Walker Lindh is requesting that his 20-year sentence be reduced. An entry on Lindh from the Mother Jones Iraq War Timeline:
[Lindh is captured on November 25, 2001 and] will be charged with ten counts, including conspiring to support terrorist organizations and conspiring to murder Americans. Maximum sentence: three life terms and 90 additional years in prison. He will eventually plead guilty to two counts: violating an executive order prohibiting US citizens from giving their services to the Taliban and committing a felony while carrying firearms. He'll be sentenced to 20 years in prison, a long sentence for a nonviolent felony conviction for a first-time offender.
David Hicks is an Australian who was caught fighting for the Taliban by the Northern Alliance. John Walker Lindh is an American who was caught fighting for the Taliban by the Northern Alliance. One could probably argue that Hicks' sentence is too light (and pretty clearly a political move designed to help the unpopular conservative Australian PM John Howard in an election year), and one could probably argue that Lindh's sentence is too heavy. Dude was an incredibly screwed up 19-year-old when he made his way to a Pakistani madrassa and began his journey to "terrorist" status.
Keep in mind that Lindh was tried and sentenced roughly half a year after he was captured, whereas Hicks was held in Guantanamo for almost five years without charge.