Abstract: Legal uncertainty over the fair reasons for redundancy and for substantial modifications of working conditions is an important factor explaining some of the worst imbalances of the Spanish employment relations system. In 2012 the Spanish legislature has passed a comprehensive labour reform, a fundamental part of which attempts to overcome that uncertainty. After identifying the main causes of legal uncertainty, this paper asks if the new role assigned to the labour courts will serve the purpose of the reform and if eventually this will succeed in bringing legal certainty to the realm of employment adjustment measures. Key Words: Labour courts, dismissal, modification of working conditions, labour reform. Legal certainty.