Judgment of the Court (Second Chamber) of 22 February 2001 in Case C-187/99 (reference for a preliminary ruling from the Supremo Tribunal Administrativo): Fazenda Pública v Fábrica de Queijo Eru Portuguesa Lda (Inward processing relief arrangements — Regulation (EEC) No 1999/85 — Rate of yield of the processing operation — Authorisation issued by the competent customs authority — Power of that authority unilaterally to alter the rate of yield)