I know Boston University Law has a study-at-Tsinghua program. I think it's a summer thing, though. And you can continue on for an extra semester at Tsinghua to receive an LLM with a China focus.
Are you familiar with the ^Hopkins-Nanjing Center at Nanjing University (NanDa)? I'm not sure if that's the 'graduate college in China' that you were referring to, but it would be a strong fit for someone with your Mandarin language and Chinese living experience plus your career interests. Sure, it won't get you in an American law firm as an associate because you don't finish with a JD at Hopkins-Nanjing. It's a 1-yr Chinese Studies certificate program with an option to specialize in Legal Studies. There's also an optional MA attached through the Johns Hopkins School of Advanced International Studies (SAIS). Grads from Hopkins-Nanjing take on sweet public, private, NGO, gov't, law jobs in China, Hong Kong and almost everywhere else. The advantages of HNJ over law school is the one-year thing and the direct Chinese connections. Your Mando skills will shoot through the roof since the classes are taught in Mando. No LSAT study and no entrance exam study. You'll need to take the Center for Applied Linguistics (CAL) Chinese exam, but you'll ace that if you majored in Mandarin and spent all that time in China. But you said family reasons are keeping you in the U.S. Hmm. Anyway, I'd recommend Hopkins-Nanjing first then maybe law school if you still wish.
/End sales pitch.