I don't see how your attorneys could argue against it.. GPU rigs, sure they should fall under the exemptions as they are freely programmable.
ASIC-based miners however are much like a cash register or hand-held/desktop calculator. Yes modern ones offer high flexibility in addressing their core functions but in the end they are fixed-purpose data devices and both are charged import duty.
So after thinking about this, would you consider the xilinx zynq chip to be programmable?