"There's no joy in this for me or our company," Messick said.
"Those of us who love the sport and love competition will always wonder what might have happened and whether he would be good enough to win [in Hawaii].
"I don't know, but we all wanted to find out.
"On the other hand, sports are governed by rules and it's by having and enforcing rules, it's the only way you can guarantee fairness."
Armstrong originally raced in triathlons as a highly-rated teenager in the late 1980s before switching to cycling.
After retiring from cycling, he switched back to triathlon and had shown strongly in half-Ironman distance races.
Armstrong was due to make his Ironman debut in June, but the WTC reluctantly decided not to let him because he was under an open doping investigation.
The WTC will review that rule at the end of the year.
Once he decided not to contest the USADA allegations and was banned for life, Armstrong could no longer consider Hawaii.
He still races in non-sanctioned triathlons.
Australia's reigning Hawaiian champion Craig Alexander said one of his big motivations this year was to race against Armstrong.
The WTC had also planned to undertake a major partnership with Armstrong and his Livestrong cancer charity before he was banned.
"We've told him ... we need to see how these next weeks unfold," Messick said.
"We're responsible for the Ironman brand and we need to be careful and mindful of that.
"We are hopeful that whatever happens, the message and the work that Livestrong is undertaking continues.
"Lance has been an enormous, powerful force for the good in the cancer community."
Armstrong has regularly trained on Hawaii's Big Island, where the Ironman is held, and there has been speculation he will be in Kailua-Kona for the race.
"I don't know, but I suspect I would know if he was here," Messick said.
-AAP
