As explosive as they might seem, ordinances are not weapons by which to cause physical damage. They are decrees or laws made to bring the populace under a suitable form of conformity. Ordnance on the other hand are indeed intended to cause explosive results.
Ordnance defined: 1a : military supplies including weapons, ammunition, combat vehicles, and maintenance tools and equipment b : a service of the army charged with the procuring, distributing, and safekeeping of ordnance 2: cannon, artillery–Merriam-Webster.com
Ordinance defined: 1a : an authoritative decree or direction : order b : a law set forth by a governmental authority; specifically : a municipal regulation 2: something ordained or decreed by fate or a deity 3: a prescribed usage, practice, or ceremony–Merriam-Webster.com