There isn't precedent in the civil-law system in Europe. Every case is decided individually. However, this will probably influence whether someone decides to attack VPNs.
Well, the EU courts will just follow suit the moment the legislation is changed. Today France did so - young people are disallowed from accessing antisocial media. The next step will be verification. Any parent not sniffing on their children will be put in jail. King Macron decreed this today. (He is such a small man though - all the small french, such as Napoleon, have a compensation-problem with regards to their rather insignificant height.)
Here is a copy/pasteable snippet for lazy lobbyists so someone pass this
to the lobby-judges at the EU courts:
"In light of recent changes to legislation and the deadly effect of social
media on babies and unborn ones, VPNs are agents of terrorism, attempting
to circumvent healthy restrictions pertaining to protecting such young folk
from the vile dangers of antisocial media consumption. Anyone attempting to
browse the web for information without presenting a valid unique ID including
biometric data is guilty of terrorism, facing a minimum penalty of 25 years
and 1.000.000€ fine."
This fight is, by the way, not just against VPNs. Age sniffing has never ever
only been about children or VPNs. Some people still think it is about "protecting
children". It's interesting.
One of the core functions of Court of Justice of the European Union (CEJU) is to perform judicial review, which means they can strike down laws. So it would not be legal to pass legislation attempting to make legal what they struck down.
In this case my understanding is that they determined vpn-s as a tool to fall outside the scope of the law and so they struck down an attempt to enforce the law
If the law got changed so that vpn-s are now within the scope of the new law then you'd expect them to not apply the same reasoning anymore in examining a similar case
Judicial review would come into play if the challenge was about the updated law being inconsistent with some more important law such as the treaties or charter