They either comply or they don't. It will be interesting to see if any of the militias will come to the aid of those that don't comply. I doubt they will.
I think people have until the end of the year (I may be wrong about that), so we won't know much about noncompliance for a while. As far as I know, there aren't any militias in Connecticut. But the Connecticut Citizens Defense League is a very principled and very active (politically, legally, and for recruitment) gun rights group which formed in 2009 and they have had some success in pushing back against state and local government. They're one of the groups suing to stop this. They've also gone from around 2,500 members just before Sandy Hook to about 8,500 now and are still growing rapidly.
They've all but declared war on every politician who voted for the law. They have always selectively endorsed candidates, but now they have taken to issuing press releases stating that they won't be supporting anyone who voted for this.
Press Release On Senator McKinney Gubernatorial Run
Groton, CT July 23rd, 2013
The President for the Connecticut Citizens Defense League (The state’s largest grass roots gun rights group) offers comments on a gubernatorial run by Senate minority leader John McKinney.
CCDL President Scott Wilson: “Senator McKinney was instrumental in implementing a historic gun control law with zero consideration for the constitutional rights of law abiding gun owners. With his deliberate act of siding with gun control supporters, there will be no support from CCDL for his run”.
The CCDL President also stated that other elected officials who went along with the Senate leader and voted in favor of the gun control law, could expect the same from the organization.