So injunctive relief will be sought before the law takes effect, and a lawsuit will result in the law being thrown out. No surprise there.
BTW, whoever wrote that isn't reading the law correctly. Specifically they ignored or didn't understand this section
- or; (2) lawfully possesses a firearm prior to
9 the effective date of the chapter of the laws of two thousand thirteen
10 which added this section subject to the registration requirements of
11 subdivision sixteen-a of section 400.00 of this chapter and knowingly
12 fails to register such firearm pursuant to such subdivision.
IOW, if you lawfully possessed the weapons before March 13, 2013, you can still lawfully possess them by registering them. So they haven't banned handguns. They've simply adopted state-wide registration of all firearms.