Tip Pooling: can it be involuntary?

I work in a fine dining restaurant which requires all front servers and back servers to pool all of their tips. The goal is to build overall effieciency and create less drama (who has the best section etc.) So say I personally recieved 320 dollars in tips, it would not matter anyways because everyone would probably recieve say.. 150. My question is: Is it legally acceptable for the employer to require that all severs pool their tips. I have done some research, but it is inconclusive as some say yes, some say only if the servers are in agreement and it is in writing. Just wondering, thanks.