The general regulation establishing the EU LFS with provisions on design, survey characteristics and decision making processes is:
Council Regulation (EC) No 577/98 of 9 March 1998 on the organisation of a labour force sample survey in the Community.
This regulation has been changed several times since its adoption, the latest changes being
Regulation (EC) No 1372/2007 of the European Parliament and of the Council of 23 October 2007 amending Council Regulation (EC) No 577/98 on the organisation of a labour force sample survey in the Community
which changes the status of the survey characteristic 'income' from optional to mandatory, and
Regulation (EC) No 2257/2003 of the European Parliament and of the Council of 25 November 2003 amending Council Regulation (EC) No 577/98 on the organisation of a labour force sample survey in the Community to adapt the list of survey characteristics.
which introduces 6 new variables and allows the wave approach for structural variables.
In addition, implementing regulations specify further detail, in particular on coding and classifications. The latest of these implementing regulations provides the codification 2009 including the compulsory survey characteristic 'income' and the general definition of reference quarters:
Commission Regulation (EC) No 377/2008 of 25 April 2008 implementing Council Regulation (EC) No 577/98 on the organisation of a labour force sample survey in the Community as regards the codification to be used for data transmission from 2009 onwards, the use of a sub-sample for the collection of data on structural variables and the definition of the reference quarters.
Of the earlier implementing regulations, the following one is of particular interest for specifying twelve principles for constructing the questionnaire:
Commission Regulation (EC) No 1897/2000 of 7 September 2000 implementing Council Regulation (EC) No 577/98 on the organisation of a labour force sample survey in the Community concerning the operational definition of unemployment.
Further legal basis for the LFS is included in regulations on ad hoc modules that fix special topics and detailed variables that are to be collected only once or in intervals of more than one year, and in regulations on statistical confidentiality that stipulate the detailed rules used for receiving, processing and disseminating confidential data.
A full list of regulations relevant for the LFS can be found in 
this file.
