1. The provisions of this Charter are addressed to the institutions, bodies, offices and agencies of the Union with due regard for the principle of subsidiarity and to the Member States only when they are implementing Union law. They shall therefore respect the rights, observe the principles and promote the application thereof in accordance with their respective powers and respecting the limits of the powers of the Union as conferred on it in the Treaties.
2. The Charter does not extend the field of application of Union law beyond the powers of the Union or establish any new power or task for the Union, or modify powers and tasks as defined in the Treaties.
What does 'implementing Union law' mean?
promoting application of principles
limitation by the powers and tasks of the Union!
The aim of Article 51 is to determine the scope of the Charter. It seeks to establish clearly that the Charter applies primarily to the institutions and bodies of the Union, in compliance with the principle of subsidiarity. This provision was drafted in keeping with Article 6(2) of the Treaty on European Union, which required the Union to respect fundamental rights, and with the mandate issued by the Cologne European Council. The term ‘institutions’ is enshrined in the Treaties. The expression ‘bodies, offices and agencies’ is commonly used in the Treaties to refer to all the authorities set up by the Treaties or by secondary legislation (see, e.g., Articles 15 or 16 of the Treaty on the Functioning of the European Union).
As regards the Member States, it follows unambiguously from the case-law of the Court of Justice that the requirement to respect fundamental rights defined in the context of the Union is only binding on the Member States when they act in the scope of Union law. The Court of Justice confirmed this case-law in the following terms: ‘In addition, it should be remembered that the requirements flowing from the protection of fundamental rights in the Community legal order are also binding on Member States when they implement Community rules ...’ (judgment of 13 April 2000, Case C-292/97  ECR I-2737, paragraph 37 of the grounds). Of course this rule, as enshrined in this Charter, applies to the central authorities as well as to regional or local bodies, and to public organisations, when they are implementing Union law.
Paragraph 2, together with the second sentence of paragraph 1, confirms that the Charter may not have the effect of extending the competences and tasks which the Treaties confer on the Union. Explicit mention is made here of the logical consequences of the principle of subsidiarity and of the fact that the Union only has those powers which have been conferred upon it. The fundamental rights as guaranteed in the Union do not have any effect other than in the context of the powers determined by the Treaties. Consequently, an obligation, pursuant to the second sentence of paragraph 1, for the Union's institutions to promote principles laid down in the Charter may arise only within the limits of these same powers.
Paragraph 2 also confirms that the Charter may not have the effect of extending the field of application of Union law beyond the powers of the Union as established in the Treaties. The Court of Justice has already established this rule with respect to the fundamental rights recognised as part of Union law (judgment of 17 February 1998, C-249/96 Grant  ECR I-621, paragraph 45 of the grounds). In accordance with this rule, it goes without saying that the reference to the Charter in Article 6 of the Treaty on European Union cannot be understood as extending by itself the range of Member State action considered to be ‘implementation of Union law’ (within the meaning of paragraph 1 and the above-mentioned case-law).