Then the citizens will either let them, or they will fight. If they fight, then the antis have no idea what they are in for. You see, they claim that no citizen militia can possibly oppose the US military, what with its possession of fighter jets, Abrams tanks, and nuclear weapons.
What they overlook is the fact that a company of 14 tanks requires 1,000 gallons of fuel to travel 100 miles. Those same tanks must be repaired every 250 hours of operation. Keeping two F-16 jets in the air for immediate support of troops on the ground requires more than 3,000 gallons of fuel per day, plus each jet requires 12 man hours of maintenance for each hour of flight. A squadron of 18 such aircraft needs more than 400 people to keep 18 to 24 of those jets in the air, along with hundreds of other support personnel.
Each of these weapons systems are wonders of technological achievement. Therein lies the weak spot. The maintenance, arming, and fueling of these systems must, over the long term, be performed inside of fixed installations, using hundreds of personnel. Unlike our war in Iraq, the fuel and spare parts would be manufactured in the same nation where the conflict is occurring.
When a government declares war against its own citizens, the gloves come off. Convoys of fuel trucks and spare parts are easy to raid, and a tank with no fuel becomes a fixed pillbox. A jet fighter on the ground threatens no one. So the military has to spend time guarding the convoys as well as the bases. For each soldier who patrols the area, several are needed to guard their fixed bases.
Once the bases are thoroughly guarded, the citizens attack the factories that make the spare parts, the electric lines bringing them power, and the supply trucks and pipelines that supply the factories and refineries. Now the military has to use the high tech weapons and equipment to guard those.
So the citizens switch tactics again, and begin threatening and attacking the factory workers and their families at home. The troops cannot be everywhere.
This is why would be dictators are so afraid of an armed citizenry, even more so than they fear a foreign army. It only took 13 months for 309,000 coalition troops to defeat the 375,000 strong Iraqi Army. After that, an estimated 130,000 insurgents fought the 176,000 coalitions troops to a 5 year long standstill, and the coalition troops had the distinct advantage of having a secure pipeline of spare parts, fuel, and ammunition.
Extrapolate that to what would happen if even a minor fraction of the estimated 100 million gun owners decided to oppose a weapons confiscation, keeping in mind that there are less than 2.5 million in the entire military, plus another estimated 1 million police officers in the nation, and at least some of those cops and soldiers could be expected to join their friends, families, and neighbors in opposing such a dictatorial move. Even so, the balance of forces will ALWAYS favor an armed citizenry over their government.
In the case of the USA, assuming that only one in 25 gun owners opposes the cops, and all of the government's forces are in combat roles with 100% participation, the government is still at a 7:1 disadvantage. Factor in the number of troops who would be needed to maintain and guard the weapons systems and their support bases, plus the forces needed to maintain commitments elsewhere, and the forces available to actually oppose a citizen militia would fall to one soldier for every 40 or 50 citizens.
As for nukes, who cares? They are useless against citizen militias.
The anti gunners who think that citizen militias are worthless clearly do not understand reality, nor do they understand why arming the citizens was the incredible stroke of genius.