"I know there are rules that are written down that we're supposed to follow, and guidelines that we're supposed to follow, but there's a difference between right and wrong, and right and wrong in my opinion should come first, always," McCready says in an interview airing Friday on ABC's 20/20.
She adds: "What I did was to protect my child, and there's not a person in the world that's going to tell me that that is wrong."
The country singer, 36, and Zander, 5, were found last Friday in Arkansas, three days after she picked him up from her father's house in Cape Coral, Fla. McCready's divorced parents have custody of Zander, but the singer has claimed her son is in physical and emotional danger staying with them.
In the new interview, McCready, who is also pregnant with twins, says she's shocked that her actions could be deemed illegal – that she couldn't "ever think that me taking my own child, that I carried for nine months, that I gave birth to in the hospital by myself, would ever be breaking the law."
She also recounts Friday's action by U.S. Marshalls to take Zander from the Arkansas home. "He was screaming, 'Please don't touch me, please don't touch me, please don't touch my mommy. Please, leave me alone, I want to be with my mommy,' " McCready says.
McCready was involved in a child-welfare hearing in Arkansas on Monday, and said she was happy with the outcome, though she couldn't talk about what the ruling was.