Can I wear my army class A uniform to a buddy’s funeral even tho he was national guard and I’m out of the service?

Don't over think it. Military Vets wear Uniforms to funerals and weddings all the time. It's not uncommon at all. I would recommend speaking to the family and asking them about it. It's their occasion as well and it is in good taste to talk about it. Just make sure your Uniform is in order , fits and you are wearing it correctly to include adhering to the grooming standard. Don't be the guy wearing a uniform with a beard and jacked up hair.

Yes, BUT...

Wear it right. Personally, IMHO that includes shaving and getting a haircut. But that is me. What *isn't* me is making sure the uniform is complete, al medals or ribbons are worn properly, it is cleaned and pressed, etc. Like you are ready for inspection.

AND

Check with the family first. They may have some specific reasons why they do or do not want uniforms there. Unless you were this guy's closest friend ever and he held you in higher esteem than his own momma and/or wife, your wants / needs for the funeral take a back seat to theirs.

Finally, military uniforms draw attention. Make sure that you do not make yourself a spectacle, even by accident. It's not about you, so don't let it become about you.

Sure, you can. If that's how you want to honor your friend.