They have gluten free soy sauce, but they were not very knowledgeable. They brought me salad after I said the dressing probably had gluten, assured me it didn't, then came and took it away again a few minutes later. They wanted to accommodate, but they didn't know what was ok or not, and very little was.
I have eaten sushi at Laku couple times with no problem. They have GF soy sauce available, just ask for it. Tell them when you order about GF issue, they will tell you how it was cooked. I usually stay away hot sauce used in hwedup-bap (raw fish, lettuce, rice) dish because I know a lot of times, Korean hot sauce has wheat in it. I bring my own hot sauce to use instead. Sushi is the best in the area.