Total grey area, but the issue depends on how much you want to roll the dice:
1) Iowa's Attorney General has an anti gun history and is unlikely to step up on an opinion, which is the next best thing to actual adjudication - we willnot have a clear ruling in Iowa without a court decision or state legislative action
2) DPS will interpret their administrative rules (which have the force of law) but would not likely offer advice on red letter Iowa Code language, which is the issue here
3) Charging someone comes down to the individual counties' political bent and the circumstances of the law enforcement interaction - I.e., you rob a bank in Johnson County with a Shockwave, the County Attorney might roll the dice on an appellate case after a trial court conviction. Discharge a Shockwave inside city limits in Sioux County, more likely to be told not to do that again. A lot also spends on the cop/department in question, how there day went, whether they can stand talking with the county attorney, etc.
4) if I lived in free parts of Iowa, I would be much less concerned. If I lived in a blue county, places with "Aldermen" or other signs of rampant corruption, I would use use caution.
Anyone got a different assessment of how this might play out? I just see an extended period of not knowing until (1) legislative action or (2) somebody doing something stupid. Either way, no resolution until July 2018 at the earliest.