Robert Rodriguez’s resignation from the Directors Guild of America has jeopardized Paramount’s development of its adaptation of Edgar Rice Burroughs’ classic SF book A Princess of Mars, Variety reported. The director of Spy Kids quit the union so he could co-direct Sin City with Frank Miller, who created, wrote and illustrated the three-book graphic novel series on which that movie is based, the trade paper reported. (Guild rules do not permit such “co-directing” credits.)