More like eight (May to January).But the militia act only formalized what had been de facto before. The preceding four paragraphs of your source:
The first test of Confederate willingness to accept the Native Guards in the spirit of true fraternity had not gone well. On September 28, 1861, word had come that Union prisoners captured at Manassas would arrive in New Orleans within two days. Their arrival was an occasion for much excitement, and the troops selected to guard the prisoners as they marched from the train station to the city prison would be afforded a great honor. General John L. Lewis of the Louisiana militia suggested that the Native Guards be allowed to escort the prisoners of war. But the Confederate commander in New Orleans said no, and white militiamen were picked instead.Despite the rebuff, the Native Guards continued to demonstrate their support for Confederate Louisiana by participating in two grand reviews- one on November 23, 1861, and a second on January 7,1862.
Enthusiasm among the Native Guards for the Confederate cause did not last long, however. Many of the men were still without uniforms or equipment, and one company had only ten muskets. Absenteeism increased when it became apparent that the Confederate authorities did not intend to provide the Native Guards with either the status or support they afforded white soldiers.
When the state legislature passed a law in January, 1862, that reorganized the militia by conscripting “all the free white males capable of bearing arms… irrespective of nationality.”
Perhaps. I was going from the April 21 organization meeting to the actual February 15th dissolution brought about by the law.
They didn't fare much better under the Feds, but at least they were given uniforms and supplies, and they fought at Port Hudson. Wikipedia is not always a trustworthy site, but here is what they had to say:
On September 27, 1862, Butler organized the Union Army's 1st Louisiana Native Guard regiment, some of whose members had also been part of the previous Confederate Native Guard regiment. The regiment's initial strength was 1,000 men.
... When Nathaniel P. Banks later replaced Butler as Commander of the Department of the Gulf, he began a systematic campaign to purge all the black line officers from the 1st, 2nd, and 3rd Regiments of the Louisiana Native Guard. He succeeded in securing the resignations of all the black line officers in the 2nd Regiment in February 1863, but most of the black line officers in the 1st Regiment and 3rd Regiment remained.
... From its formation in September 1862 until early May 1863, the 1st Louisiana Native Guard largely performed fatigue duty–chopping wood, gathering supplies, and digging earthworks. From January 1863 to May 1863, it also guarded the railway depots that ran along the rail line between Algiers (now part of New Orleans) to Brashear City (now called Morgan City). By this time, its numbers had diminished to 500.
In mid-1863, the 1st Louisiana Native Guard, along with the 3rd Louisiana Native Guard, had its first chance at combat and participated in the first assault at the Siege of Port Hudson on May 27, as well as the second assault on June 14. ...
In June, 1863, the 1st, 2nd, and 3rd Louisiana Native Guard Regiments were dissolved and folded into the newly formed Corps d'Afrique. Perhaps 200 to 300 of the original 1,000 members of the 1st Louisiana Native Guard made this transition.
Poor treatment by white soldiers and difficult field conditions had lead to the resignation of many officers and the desertion of enlisted soldiers. In April, 1864 the Corps d'Afrique was dissolved and its members joined the newly organized 73rd and 74th Regiments of the United States Colored Troops of the Union Army. By the end of the war, 175,000 African Americans served in 170 regiments of the United States Colored Troops. In contrast to the 1st Louisiana Native Guards organization, all field and line officers of the United States Colored Troops were white. By the end of the war, approximately 100 of the original 1,000 members of the First Louisiana Native Guard were members of the 73rd and 74th Regiments.
There is a continuing legend that the Confederate Army's Louisiana Native Guard regiment organized in May 1861 was reformed in its entirety as the Union Army's 1st Louisiana Native Guard regiment in September 1862. This assumption is incorrect. Of the nearly one thousand enlisted Confederate Native Guard members, only 107 were recorded to have enlisted in the Union "Native Guard" and only ten of 36 officers served the Union. The legend of continuity of regiments is considered by many to have been a propaganda ploy by Union General Benjamin F. Butler.
Here's some information on the resignation of black officers of the Native Guards under Union General Banks: Link (scroll down to see the roster). Many of them served from September 27, 1862, to February 19, 1863, the date of the so-called "mass resignation." Hmmm, let's see. That's less than five months service.
On February 18th or 19th, 1863, General Banks reportedly implied that he would not object to letting enlisted Negroes resign and return to their plantations if they so wished (Source: New Orleans Daily Picayune, February 20, 1863). Perhaps that date ties in to the "mass resignation" and ties in to the low numbers of Negroes that made the transition to the Corps d'Afrique in June 1863. That and the Port Hudson battle, of course.