It depends on the laws of your state and how your particular device works. In every case that I have seen you just need to provide a receipt for the work and it should never get to a judge.
Some interlocks require the car battery in order to store data. Others look at disconnecting the battery being part of bypassing the unit. As long as you have a receipt your should be fine – I had a manager at one interlock place tell me to just buy a battery cable and keep the receipt in case I ever had to disconnect the battery on my own for any reason.