Yes, a judge could hold them in contempt and jail them for some time. That's the only legal option.
It's possible they could seize some assets as part of the contempt charge, but there are already plenty of legal groups that would jump at the opportunity to represent them pro bono.
The other suggestions you offer are, to be blunt, those of a conspiracy nut.
Not some time, there's no limit. It can be extended arbitrarily.
All the others points I made in the legal section are indeed legal and have been used in the past though they are indeed unusual.
The FBI can't take away the person's children. --Even if he's put in jail, the other parent would retain custody. The FBI would have to convince social services to remove the children from the home, and family court judges aren't overly likely to go along with that.
The FBI could potentially convince a psychiatrist to have a person involuntarily committed for a short time for observation, but they can't force any doctor or hospital to put the people on drugs or otherwise force some form of treatment on them if there's not diagnosis of mental illness.
The FBI doesn't get to tell the IRS to make claims about a person owing an astronomical sum. I suppose they could fabricate evidence and give it to the IRS, but then the individuals responsible would be performing illegal actions and risk being sent to prison themselves. Most members of the law enforcement community are decent people and aren't willing to do that type of stuff.
Given the importance of the situation it seems it is very likely it is going to happen just here. It's up to the judge(s).
>and family court judges aren't overly likely to go along with that.
It's up to the judge(s).
>The FBI could potentially convince a psychiatrist...
This is just redirecting pressure to a different person, keep doing it until you find that someone who will buckle.
> Most members of the law enforcement community are decent people and aren't willing to do that type of stuff.
Just like above, most are honest, but you only need one that isn't.
If you think all of those are impossible by the US government, take a look at you know where, where torture doesn't happen, and no-one was prosecuted for torture that didn't happen.
Black and white thinking. The government does something you disagree with, so suddenly now it's natural to expect them to wield literally every tool of state power against you to make that happen.
The government, after all, is not a singular entity. Its made up of many checks and balances and institutions that often act in disagreement with one another.
This, and other techniques you describe, have been used by the FBI in the past but as far as I know only against the relatively powerless. It seems silly to think the FBI would do it in this case.
If the FBI started doing that to employees or ex-employees I suspect Apple would leave the U.S.
The key point here is that if the USG find a way to force Apple and Apple engineers to do this work then the government, by default, they must have too much power.
This is always better but they don't even need to find it. That's just a bonus.
They can just fabricate it. Assange is still in effective house arrest because someone apparently was a victim of "sex by surprise".
If that were actually implementable against large powerful corporations universally, we would not have had a bailout after the derivatives bomb. As it is, not even the ratings agencies got nicked.
#Legal:
* Judge orders them to comply, if they refuse they can be considered to be in contempt and incarcerated for a de facto arbitrary period of time at the judge's discretion (vide https://en.wikipedia.org/wiki/H._Beatty_Chadwick incarcerated for contempt for 14 years just because the judge suspected he had funds that apparently he didn't have, also Terrell Geiger http://articles.chicagotribune.com/2011-10-07/news/ct-met-lo...)
* Civil forfeiture. The state can just de facto steal every single item those people have and leave them unable to fight that in court (not that it would make much difference)
* Involuntary commitment. They can just be committed into a psychiatric institution where they can be drugged against their will and even tortured. This can be extended to an arbitrarily long period of time
* They can have their children taken away
* IRS can just accuse them of an astronomical tax debt, take all of their possessions and leave them effectively unable to get legal representation (not that it would make much difference)
#"Illegal":
* Just detain them in a secret facility and do with them as they dam well please
TLDR: The state does with you what it damn well pleases and there's nothing you can really do about it. Granted this usually doesn't happen but that's just because the stakes usually aren't that high.