Relative told me a federal law states only a registered nurse can give insulin shots thus we have to put my aunt in a home. Is this a law?

As a 65 year old diabetic I can tell you anyone can administer Insulin

I believe that was only in schools/daycare and there are all kinds of exceptions. Check your state for laws about who can administer insulin injections. We gave Mom her shots for years without question from anyone.

Thats odd, I gave my mom insulin 2 times a day, She was a diabetic and had dementia.

Anyone can assist with insulin.
VERY common family members
Giving insulin.

Just ask your doctor or pharmacy.

Any one can administer insulin injections at home provided they have been properly instructed. They should also be aware of the side effects of insulin injections.

Any idiot can learn to give insulin, yes. But if you are a CNA in a nursing home and you measure out and inject the insulin, you lose your license.
Check with your state health department, some allow LPN's some require RN's to do this.

If you HIRE someone to give the insulin they must be a qualified nurse. If the patient is ok with a relative doing it then only such training as how to do it properly is required.

I would talk to the doctor, and he can train you to give shots, So long as the doctor knows that you are giving her her shots and that you know how to do it. Tons of family members give insulin shots. The thing you need to learn is how to do it in a sterile manner.

I give myself insulin every day. There is no Federal law -- such a law would make diabetes management impossible. Please ask your doctor for guidance and instruction.

Giving the benefit of the doubt, your relative is mixing up some things he or she has heard, that may be sort-of true in other situations. (Or, not giving the benefit, he/she has some motive to want to see your aunt in a nursing home.)

I don't think I would take medical or legal advice from this relative!