Is the invalidity of the Data Retention Directive completely retroactive and what are the implications w.r.t. the Charter of Fundamental Rights?

Question

On 8 April 2014, the Court of Justice of the European Union (CJEU) declared the 2006/24/EC Data Retention Directive (DRD) invalid because it violated the rights guaranteed by Articles 7 & 8 of the Charter of Fundamental Rights of the European Union. The CJEU's press release (PDF link) clarifies the retroactive effect of the invalidity in a footnote:

Given that the Court has not limited the temporal effect of its judgment, the declaration of invalidity takes effect from the date on which the directive entered into force.

While the DRD entered into force in 2006, the Charter was only formally incorporated into the EU treaty framework on 1 December 2009. Though the Charter has existed since 2000, its legal status was uncertain prior to incorporation.

How can the DRD be retroactively invalid prior to 1 December 2009 when the invalidity is based on the Charter incorporated on that date?

Trying to find the answer to this question led me down a number of related questions that may help, but I've not found a definitive answer to any:

• Is the press release incorrect? When CJEU invalidates a statute without specifying date, does that really imply complete retroactivity? While this decision is silent about it, is there other case-law that might help here?
• Has the Charter been determined to have legal force before its formal incorporation by the Treaty of Lisbon? Would that have been the presumably treaty-level force necessary to strike down a Directive?
• Recital 22 of the DRD specifically cites compliance with Articles 7 & 8 of the Charter, but are recitals a sufficient basis for invalidating the Directive's substantive Articles? The CJEU decision quotes the recital, but doesn't explicitly make use of it in its ratio decidendi.

Answer 1

When a statute is invalidated by judicial review it is typically void ab initio

Since the government lacked the power to enact the law in the first place, the legal effect is that the government never enacted the law.

However, ...

When a statute was valid and then became invalid because the adoption of a higher law made it invalid (intentionally or otherwise), then it was valid while it was valid because the government did have the authority to make the law and is invalid from the point where the invalidating law was adopted.

So, ...

It remains uncertain. When the court rules on a case where it matters, it will be resolved.