i wasnt watching the news at that time
why were they taking guns?
Because they thought civilians with firearms would cause mayhem because of course civilians can't be trusted with firearms. The reasons you'd expect - the same tired contempt the government has for independent citizens. However, there was also potentially a racist element carrying them around. Here's the story of that:
For all these reasons, Nagin and the New Orleans PD borrowed a page right out of the supposedly "paranoid fantasies" of the gun community and confiscated firearms from citizens.
I am not a fan of vigilantism and am really opposed to racism and racial intimidation, but that is no reason to leave people completely defenseless in a natural disaster situation (this would include blacks, obviously.) Of course some private citizens will be irresponsible with their weapons. One of the many reason to leave civilians with guns alone is to protect themselves from these idiots as well.
You can imagine the potential in a natural disaster scenario for:
(a) Looting, crime, and armed robbery.
(b) Gang violence
(c) Certain far right-wing types
taking advantage of the lawlessness to form their own paragovernment (for lack of a better term) which may or may not have legitimacy and may or may not behave in a just manner. I am on several survival boards and some of those people - not all of them or even most of them - but a minority of them - really creep me out.
To be honest, I am armed for possible resistance to all three of these about equally, should such an event occur. Don't want an opportunistic, paranoid militia (I do not oppose all militias - just the loony ones), gang member, or looter in my home or anywhere near my family.
how did they get away with it?
I guess people didn't want to shoot at police who were doing the confiscations. Normally civilized people try to avoid this kind of thing. Not saying what anyone should do, but I think it makes sense to cache weapons for this circumstance.
have they since been given back
The NRA sued (and won) to force the issue. Many of the weapons went unclaimed, and some were rusted and corroded beyond recognition.
The NRA made a pretty big deal about it, as they should.
This was terrible for the city of New Orleans, but it provided lots of ammunition (in a manner of speaking) to those who have maintained for a long time that the government (in this case local government) would do this in a crisis.