Did you also read the wikipedia link? The relevant portion of that page provides:
*Confiscation of civilian firearms
Controversy arose over a September 8 city-wide order by New Orleans Police Superintendent Eddie Compass to local police, U.S. Army National Guard soldiers, and Deputy U.S. Marshals to confiscate all civilian-held firearms. “No one will be able to be armed,” Compass said. “Guns will be taken. Only law enforcement will be allowed to have guns.” Seizures were carried out without warrant, and in some cases with excessive force; one instance captured on film involved 58 year old New Orleans resident Patricia Konie. Konie stayed behind, in her well provisioned home, and had an old revolver for protection. A group of police entered the house, and when she refused to surrender her revolver, she was tackled and it was removed by force. Konie’s shoulder was fractured, and she was taken into police custody for failing to surrender her firearm.[79][80]
Angered citizens, backed by the National Rifle Association and other organizations, filed protests over the constitutionality of such an order and the difficulty in tracking seizures, as paperwork was rarely filed during the searches. Wayne LaPierre, CEO of the National Rifle Association, defended the right of affected citizens to retain firearms, saying that, “What we’ve seen in Louisiana - the breakdown of law and order in the aftermath of disaster - is exactly the kind of situation where the Second Amendment was intended to allow citizens to protect themselves.” The searches received little news coverage, though reaction from groups such as the NRA, the Second Amendment Foundation, and Gun Owners of America was immediate and heated, and a lawsuit was filed September 22 by the NRA and SAF on behalf of two firearm owners whose firearms were seized. On September 23, the U.S. District Court for the Eastern District of Louisiana issued a restraining order to bar further firearms confiscations.[79]
After refusing to admit that it had any seized firearms, the city revealed in mid-March that it did have a cache of some 1000 firearms seized after the hurricane; this disclosure came after the NRA filed a motion in court to hold the city in contempt for failure to comply with the U.S. District Court’s earlier order to return all seized firearms. On April 14, 2006, it was announced that the city will begin to return seized firearms, however as of early 2008, many firearms were still in police possession, and the matter was still in court.[79] The matter was finally settled in favor of the NRA in October 2008. Per the agreement, the city was required to relax the strict proof of ownership requirements previously used, and was to release firearms to their owners with an affidavit claiming ownership and a background check to verify that the owner is legally able to possess a firearm.[81]
Louisiana legislator Steve Scalise introduced Louisiana House Bill 760, which would prohibit confiscation of firearms in a state of emergency, unless the seizure is pursuant to the investigation of a crime, or if the seizure is necessary to prevent immediate harm to the officer or another individual. On June 8, 2006, HB 760 was signed into law.[82] 21 other states joined Louisiana in enacting similar laws. A federal law prohibiting seizure of lawfully held firearms during an emergency, the Disaster Recovery Personal Protection Act of 2006, passed in the House with a vote of 322 to 99, and in the Senate by 84-16. The bill was signed into law by President Bush on October 9, 2006.[83]*
Again, yes, authorities did confiscate guns after Katrina.