Haw, a London native and former merchant seaman, began his protest in 2001 against Iraq sanctions. His father, who served in World War II, killed himself 20 years after he was one of the first Allied soldiers to view the Bergen-Belsen concentration camp.
Another peace camp, Democracy Village, was ruled unlawful last year. Haw argued successfully his own encampment was separate, extending his stay by a few months.
"Parliament Square Gardens is not a suitable location for prolonged camping," Judge Wyn Williams said in the High Court decision.