..[For example:]If the parents of a newly born fourth were brought before a jury – though all the facts and the law were established – if the jury believed the law itself to be repulsive, it could acquit thereby nullifying the law.
These are very deep waters. The doctrine of nullification -- whether state or judicial -- is like a shard of glass: it will almost certainly cut the hand that wields it. First of all, if a law is " irrational or outrageous", how did it pass into a law? Who sponsored it? Who backed it? Who voted for it? If this law could be described in one word as "repulsive" why would any one in Congress vote for it? These elected men and women have to face the voters every day - to laud in their approval or tremble under their frown -- either in person, through telephone, email, letters,etc. Surely the representative would think,
"This proposed law is ridiculous. No, worse. It's repulsive. If I vote for this thing the folks back home are going to run me out of town..."
I understand you mean your example as just that -- an example, but while anything is possible, I suspect the passing and signing into being a law that would be considered by a majority of Americans as "repulsive" is very small. No, nine times out of ten nullification is not driven by moral outrage but by friendly juries persuaded to go with the interests of the defense.
And last but not least, let us not overlook the semantic trip wires:
"... a government which has become irrational or outrageous, such as prosecuting individuals for non-compliance to a repulsive law..."
"A" government,i.e. state, or, city, or county, or federal? or "The" government, i.e. every form of government regardless of size and location? Also, in mandating/passing these "repulsive laws" could an elected government -- say, the State -- use a non-elected branch of that government [bureaucrats] as an excuse? Could it use compliance with/for a Federal mandate as an excuse?
Then come the tedious questions of:"How,and who and by what right, are terms "irrational"and "outrageous"? It may seem pettifogging to us but to a hungry, sharp witted lawyer it could mean getting that summer home by the lake.
If representative governement is working the way it was intended, then it is unlikely there will be "irrational or outrageous" laws. Nevertheless there are representatives who say one thing to their constituents when running for election and re-election and do quite the reverse when they are in D.C.
As I recall, that was the complaint which sank Tom Daschle.
The example I used was whimsical and based largely on the Chinese mandate of only one child per family. It would take a truly extreme left wing government to come up with such a law.
Perhaps a more "real world" example would be the Federal government outlawing private ownership of all kinds of guns. No doubt people could and would be successfully prosecuted in New York, California or Massachusetts where the public would generally agree and/or acquiesce.
However, when it comes to that particular right there are large numbers of people who will not acquiesce. If they are in the majority - such as in most places in Texas, Montana, etc. - then I wouldn't hold my breath for a successful prosecution. In those places the jury pool would likely acquit no matter what the facts or law say.
As betty boop observed, the jury cannot nullify a law across the board - but it can make the law of no effect case by case, time and again, by acquittals.
So far there has not been a law so repulsive that parts of the country would resort to such legal rebellion. But the option is there and the only remedy for the government would be to remove the Constitutional guarantee of a jury trial - and that would put the entire crisis before each and every state to ratify.