Is it legal to mail green chile?

You should be OK unless green chile means weed.

Should be ok since it is within the US. Call the mail service you will be using and ask about mailing perishables. Most rules regarding food have to do with bringing insects into the country that may not be already here.

I would look into it carefully. I don’t know why but I have a hunch it’s not legal. Agricultural products have some strange rules.

It really depends on the laws of the state you’re sending to. California, for instance, is very strict; they chiles from some parts of NM, but not from others. Even then, a certificate of inspection is required.

Fresh or canned?

I did not even think to ask canned or fresh, I am assuming fresh, canned would be no problem, but I know I should never assume. It looks like it is ok according to this USPS link. I would still call. Post office is usually very helpful.

Since you can buy green chile seeds on eBay, I’d say it’s legal.

Depending on what parasites are present in the NM chilis some chili growing states may have quarantines on fresh chilis.