Kid Rock was legal though because he paid for the privilege by clearing the samples and paying the fees to the Big Media leeches to use the melody/chord structure.
Not sure who the "Big Media" is that owns the copyright to Sweet Home Alabama, but he shared the publishing rights for "All Summer Long" with Skynard and Zevon. Skynard even toured with him after the release.
The interesting thing about when Rock plays other bands' music in concert, he makes a point of shouting his appreciation for them allowing him to do so. I think that's why they let him do his thing.