The Constitutions of Melfi or Liber Augustalis, was a legal code promulgated on 1 September 1231 from the castle of Melfi, (nowadays in the province of Basilicata, Italy), by the Holy Roman Emperor Frederick II. It restricted the power of the nobility and strengthened the power of the king. All freemen and citizens were declared equal before the law. As far as labour was concerned, the royal bailiffs were ordered to set maximum wages for various occupations, mostly artisans but also grape-gatherers and reapers, and to issue heavy penalties to those who demanded or paid higher rates. Probably this legislation served to protect the interests of the urban elite. No earlier examples of such government measures have been identified in European history.
Catharina Lis and Hugo Soly, Labor Laws in Western Europe, 13th-16th centuries: patters of political and socio-economic rationality' in Working on Labor, 2012, 299-321, discuss these and other labour laws formulated by the public authorities in medieval Europe.