Follow the storyline until you can get into House zu Heltzer, then you can ally with them. You have 3 more missions after the temple. You'll do Arborstone for the Kurzicks, Boreas Seabed for the Luxons, then Sunjiang District back in the city.
what snowduck said. it's annoying. I wanted tojoin the luxons with my guild, and I was in that outpost leaning against cavalon. yet I had to do 2 quests and a mission >.>