You have probaly heard you shouldn't. Many trainers say: wrong! Of course you can play tug of war -- but the caveat is, only play it with a polite, self-controlled, correctly trained cavalier. If your dog does not understand 'take it' and 'drop it', can't sit-stay, doesn't know 'wait', gets easily overexcited ... then you have some tasks before you to get your dog to the point where tug of war serves as a great exercise outlet rather than potentially, a dangerous level of stimulation that could encourage biting.

This is an excellent read on tug of war from the San Francisco SPCA:

http://www.sfspca.org/behavior/dog_library/tug.pdf