i once got pulled over in seattle on my brakeless fixie for running a red light. the cop was mostly focused on my bike rather than the law i actually broke (running the light) and was sweating me for not having brakes. i told him i did, in fact, have a rear brake. it was a foot brake. he asked me to demonstrate, so i did a couple skids for his entertainment and he let me go.
i don't recall what the actual brake laws were up there, but i remember seeing a few fellow fixies running brakes that weren't even hooked up. iirc, the law just stated you must have a brake, and didn't go into where it had to be located or if it actually functioned as a brake.