Can you burn a song that is no longer available for sale onto a CD without violating copyright laws?

If you already own a copy of the song, then copying it from a digital file to CD is not a problem. Copying from vinyl to tape or from tape to some other medium or from a hard drive, which can fail, to a CD or DVD, which is durable and serves as a backup, is considered fair use. But if you never paid for the tune in the first place, well, that's another kettle of fish. If you contact the copyright owner, he may give you permission. You would need permission of the composers, performers and producers to use their copyrighted works as well as their trademarked names. Furthermore, even if you may qualify for the exemption of "fair use" for limited copies made for your personal use, you may not sell those copies (or even distribute them freely) to others without the risk of having to explain your actions in a federal lawsuit.