Are racking labels a legal requirement?

Location labels are not, but load marking is. Annex I, point 2.15 of Directive 2009/104/EC requires that work equipment bear the warnings and markings essential to ensure the safety of workers, and EN 15635 requires a printed load notice to be provided with the equipment and permanently displayed on or adjacent to the racking. Location identification labels are an operational choice; the load notice is not.