There are four Green Lanterns from Earth.
Two of them, John Steward and Hal Jordan, are the Lanterns for Earth's sector.
How did the Guardians choose who would be an Honor Guard and who would be an active lantern? It seems to me that Kyle is an obvious choice for Honor Guard (refounder of the Corps and all), but why was Gardner chosen as an Honor Guard over Jordan or Stewart?
The Honor Guard are a collection of Green Lanterns chosen for their skill, bravery and the quality of their previous performance in their duties as Green Lanterns for their sector. The title of Honor Guard was introduced during the Tales of the Green Lantern Corps story arc. The Honor Guard are Green Lanterns without assigned sectors able to go where they need to as free agents.
Hal Jordan was originally chosen for the Honor Guard and politely refused indicating he was just "one of the gang." During the Green Lantern Corps: Recharge story arc, Guy Gardner ended up chosen for the job since he was already working as a trainer of the new Green Lanterns, had experience as a field commander and was considered a highly experienced Green Lantern. His tenure as a member of the Honor Guard was short as he was replaced by John Stewart, whose overall performance as a Green Lantern was also considered exemplary. By the end of the story arc, Kyle and John were both members of the Honor Guard.
2 main factors contributed to this. The first is the incredible importance of Earth. As the keystone to the 52 parallel universes, it is of paramount importance that Earth be protected. The second is that Earth has had multiple Green Lanterns, and all of them performed admirably. So when the Corps was being reformed, they were all inducted and provided special status.
