I have just purchased a house, where the gas line for the dryer is copper. It was run in an unprofessional manner, in that it runs up from the basement, and then along a door threshold, and finally through a wall. The laundry room is built on a slab. Are there any rules (or safety concerns) about running a new gas through the wall, into the attic, and then dropping it down through the wall?

Are there any rules (or safety concerns) about running a new gas through the wall, into the attic, and then dropping it down through the wall?
That's the way I would do it. The way the line's run now is unacceptable. Good luck, Tom

In my area of operation, the copper pipe use for gas line would not fly any more. Same goes for aluminum pipe.

Yes, gas line can be ran through walls and ceilings. It can be rigid pipe (black pipe) or Trac Pipe ( yellow flexible pipe). There are certain rules that have to be maintained during installation including pipe supports. Rigid pipe can be exposed and installed surface-mounted. Trac-Pipe would need to be covered to prevent accidental damage to it.

Since you just purchased your house, you should have inspection done prior to signing your closing papers. The inspection report will tell you if this gas line is OK with local plumbing Code or not.