I suspect the facts of "the real story" aren't far from what facts are presented in the Reuters article. Thousands of immigrants who are required by a new law to register with the INS did so on Monday, as the last day to comply. Many of these people were then jailed (or "detained" if you like the polite word better. I'd rather be arrested than detained, myself. When you're arrested at least you get a lawyer, court date, etc. We have rules on how to treat arrested people, whereas you can "detain" an immigrant virtually forever).
Why were they jailed? Not much in the way of facts on this one. I would guess that the vast majority of them were jailed because their immigration papers were not in order. In some cases, that's probably because the immigrant neglected a step in the process of renewing a visa, or deliberately stayed in the country even though they were aware that they could not get their visa renewed.
In a lot of cases, I'd bet it's a problem on the INS's end -- the INS is hopelessly overworked for its funding level, and our immigration laws are a horrid, tangled, bureaucratic mess that are a nightmare to comply with and to enforce. (I'm sure Koogrr or Francisco can offer better testimony than I on this point.) So some of these people undoubtedly applied for renewal 18 months before the expiration of their green card and now, two years later, they're still waiting to hear "yea or nay" from the INS. And a few of them are doubtless in the country on perfectly valid, current visas, but the INS has gotten something shuffled onto the wrong pile and now thinks that they're illegal.
And in a few cases the detainees are people with outstanding warrants for their arrest, or who have been mistaken for people who are wanted. I doubt that very many of them are. If you thought you were wanted for a crime, would you come to a government agency and be sure to get yourself registered?
Voice of America says here that "most foreigners detained this week in California while trying to register under new immigration laws are out on bail."
I'm not sure whether I'm glad that they've been released, or disturbed that hundreds of people had to post bail for having an expired green card.
Mind you, I'm one of those people with a violent distaste for our current immigration laws, and I am appalled at the way America routinely treats immigrants, legal and otherwise. So I've got a lot more sympathy than most for those who haven't jumped through all the right INS hoops.
So. I hope this gets straightened out to everyone's satisfaction.
Moreover, I hope it gets lots of press and people upset. Better that we stir a furor over 500 men being jailed for a week than waiting for 10,000 to be marched to be packed off to "relocation" camps before we go 'Hey, maybe this is a bad thing ...'