It is not possible to lock elements to certain layers in ArchiCAD .. anything can be placed on any layer and there is really nothing you can do about it (other than establish and train people in CAD standards).
As whatever says one way would be to define a Favourite with the wall settings you want (Composite, Layer, Height, etc). This can then be accessed via the Favourites Pallette.
cheers,
Owen Sharp
Design Technology Manager
fjmt | francis-jones morehen thorp
iMac 27" i7 2.93Ghz | 32GB RAM | OS 10.10 | Since AC5