Mount Gas Oven Range
This depends on where you're located; you need to find out what your local codes are.

Generally, you will need to at least install an anti-tip bracket so there's no way the range could fall forward on someone -- a kid climbing on the lowered door, an adult falling on it, whatever. The usual design anchors one of the back feet of the range to the floor, not to the wall -- your range may be set up differently, or your region may have different concerns (earthquake, for example).

If you don't believe your inspector, check with the local building-permits office, who can probably tell you what code requires... or check with a local appliance store or repair shop.