The Role of L1 in CLT

Ch.3 provides helpful guidelines for designing communicative activities that focus on fluency and authentic practice. Most of you can see the benefits of using communicative practice to motivate learners and fulfill their learning needs. I have a question though. Remember I talked about the relation between L1 and L2 last Tuesday. Since our students are so eager to use their native language (i.e. Chinese) in the classroom, are we going to ask them to take off all L1 and use English only in any classroom communicative practice? Would that be practical? How are we going to enforce it? How about the low beginners? I guess this is a common problem for most mono-linguistic classrooms like ours. Do you have any suggestions?