That is always a tough situation. I would recommend that you approach a professor that you particularly liked and be honest, tell them that although you did not participate as actively as you would have liked, you truly enjoyed his or her class and would be honored if they would write a recommendation on your behalf. The worst thing they can say is no. Most professors get questions like this all the time so it is not something they are not expecting. It would certainly be helpful if you could provide them with a resume or writing sample to remind them of your work. You can also mention, if applicable, how interested you are in research or other writing the professor is doing. And, if the professor attending the school you are applying to or has any other connection, they might be honestly thrilled to help.
Don't take shortcuts when it comes to recommendations though - you don't want to start off your legal career on a bad foot before it has even begun. Best of luck!
Alisa Greenstein | Veritas Prep Admissions Consultant | www.VeritasPrep.com/law