you don't need to be an engineer to sit for the patent bar. my boyfriend does IP law and he took the patent bar. his UG is english.
however, you can take the patent bar if you are NOT a jd if you ARE an engineer, thereby making you a patent agent.
if you have a jd, then you are an atty who is also a patent agent. you would be able to be a patent agent in any state without having to retake, as opposed to the regular bar.