So if a Southern state determined that the Civil Rights Act exceeded federal authority, it could continue to discriminate.
How well did that work for Governor Wallace?
You need a copy of "Reading Comprehension for Dummies," since it is stated clearly, several times, that nullification would not apply to legitimately adopted laws (passed by Congress according to Constitutional Rules.)
It would apply to "pretend laws," aka 'Executive Orders.'
I have always found that excitable immature types, are quick to read and slow to think, and put mouth (or keyboard) in gear before engaging the brain. An they always preface their profound thoughts with the non-cerebral "SO..."