From the Seattle Weekly Blog:
Although it becomes legal this week to possess one pound of "marijuana-infused product" or 72 ounces of marijuana-infused liquid, officials say Initiative-502 doesn't open the door for restaurants to plate up pot.
. . . But the clearest prohibition may be located in the state's food code, which bars commercial food producers from using any ingredients which aren't approved for human consumption, such as marijuana. "It doesn't appear that's going to change," Moyer says. Although the rules committee could recommend adjusting the code, it might be difficult to square those changes with food safety concerns: Since marijuana remains illegal under federal law, there are no plans for the U.S. Food and Drug Administration to inspect or approve marijuana-infused products.