I'm not defending Deerfield, or neighboring Highland Park which enacted a similar law in 2013, but the ordinance doesn't say a person can't own these items, just that they can't be possessed, sold, or manufactured in Deerfield.
There are plenty of storage places in close proximity to these areas where the guns, magazines, etc., can be legally stored. Granted, it's a pain to have to travel to get your guns, but it's better than giving them up or risk fines.
I was a police officer many years ago in Lake Forest, which adjoins both Deerfield and Highland Park. I don't see a door-to-door search for prohibited items happening, but I foresee the probability of a gun owner being cited/fined when they become the victim of a burglary, and one or more of the stolen items are prohibited under Deerfield's ordinance.
And this ordinance doesn't restrict revolvers, so it could be a boon for Smith and Wesson to keep building their line of home defense revolvers.