Quakers are illegal in California, although unfortunately, idiots still choose to take them there. Not worth the risk, IMO!
In other states, as cnyguy mentioned, a leg band may be required in order to keep or sell them. No restrictions in South Carolina!!!
https://www.petcha.com/where-can-you-own-a-quaker-parrot-infographic/
Regardless, some birds do have leg bands and they are removed, where-as many others do not have leg bands and never have. My mitred conure has a closed leg band, and thanks to his leg band, I was able to find out his exact age (was told he was 2 years younger than he actually is), find out his breeder (who only bred mitreds once!) and also find out that his parents were wild caught imports. My ARN *HAD* a leg band, but it was removed because it was an open leg band. Due to the info on it, I was able to find out that she's more than likely a wild caught parrot imported May of 2013. Many people assume that her age is a typo if she is in fact a wild caught import so she must be 26+ years old... All I know is that she's probably at least 5-6 years old but who knows her true age.... My cockatiel does not have a leg band and never had one. Many other birds I've had never had leg bands either. I often wish to know more about their history and lives but am often limited by what little info I may be able to glean from past people...