You can purchase your citrus from an approved citrus nursery that is certified to import citrus into Alabama or you can purchase your citrus from an Alabama nursery that is in the same citrus quarantine area as the one you live in. You can view the Citrus quarantine maps found on the citrus page on the Plant Protection website.  Basically, if you live in any one of Alabama’s 67 counties, you can purchase citrus from any nursery in any of those counties except for Baldwin or Mobile counties.  Nurseries in Mobile may only sell citrus to residence in Mobile and Baldwin counties while nurseries in Baldwin may only sell to those that live in Baldwin.  There is one noted exception.  One Baldwin County nursery has a USDA-APHIS approved screen house that permits them to export out of Baldwin County.  Your safest bet is to buy your citrus from a trusted local nursery or Garden Center in your area.  If you wish to purchase citrus from out of state, the nursery you buy from must have a USDA-APHIS approved facility and follow USDA Citrus Nursery Stock Protocol.  Those nurseries are always changing so you will need to inquire about their status before you purchase your citrus trees.