Some states, mine (Wyoming) for example, are not big on certification.
First you don't need a permit to carry in the state, but you can (and its suggested you do) get a permit which covers you in many other states.
To get a permit, you take a safety course by any LE firearms instructor, OR, NRA instructor, OR, have a DD 214, OR have been a LE officer, OR, have completed a Hunter Safety course, OR, have competed in any type of firearm competition and produce a copy of the bulletin from that match with your name on it.
Many local clubs provide firearm safety training and no or low cost. The idea is to keep the right of Self Defense from becoming a rich man's game.
Not gonna argue whether its right or wrong. But this state tends to want to leave the people alone as much as possible.
I happen to agree with this policy, but I also believe that its up to the individual to seek as much training as possible.
We have more guns per capital then any other state and do have a relatively low crime rate.
I don't believe one can get enough training. I also don't believe a knowledge of firearms and their use, make one a teacher. I got my first formal firearms instructor course about 40 years ago, and many more since, as a LE officer in Anchorage. But in Alaska, regardless of how many classes you took, the Alaska Police Standards Council would not certify you as an instructor until you attended the FBI Instructor Development Class. That's not just firearms, but any subject one would teach cops.
I don't care how long you been shooting, how long you've been a cop, how long you've been in the military, all the training and experience in the world, or what certificates you have, if you cant present the material, (shooting, Self Defense or anything else), identify problems and disabilities, you are just another shooter.
Anybody can be taught, regardless of any disabilities. Its like Gary Anderson says in his CMP Master Instructor's course, "THERE ARE NO HOPELESS SHOOTERS" but there are hopeless instructors.
The best example of the most challenging course I ran across is conducting machine gun schools to Alaska Native Guard Units. They are great people, but they are shy, its hard to get them to open up, near impossible to get them to ask questions so its difficult to judge whether they are gasping the subject or not.
Machine guns isn't just about putting rounds down range with an automatic weapon. You have to know the MIL System. There really isn't that many educated, experienced shooters who really understand it. Try teaching it to individuals, most don't have an 8th grade education. You have to gain their trust, you have to get them to open up. To do that you have to understand their culture. Best way is to live with them, show them you are their equal, not their superior, because in their environment, you are inferior.
Its the same with any group of students, not just with firearms and self defense, but every subject.
Don't be afraid to listen to the students, I've learned a lot from students that I apply to other classes and subjects.
A certification is nothing if you cant present the subject, and always remember, you method isn't the only method, and may not be the best. The worst thing an instructor can possess is an EGO. Be humble, don't be afraid to learn as you teach.
Anyone can learn to shoot, not every one can learn to teach.