The problem is when you analyze what this means in practice. In Belgium consensual sex is legal IF
1) both parties are 18 and the age difference is less than 2 years
2) both parties are both older than 14 years (used to be 16)
3) there is no "power relationship" between them (this requirement actually drops when one, not both, turns 18)
Unfortunately ... now apply these rules to a sexual relationship between a 14 and a 17 year old.
a) 1st year: legal, any images are not CSAM
b) 2nd-5th year: illegal, any images are CSAM
c) 5th year onwards: legal, images not CSAM
Law sucks. It used to be worse, this is an actual improvement over the previous situation, but ...
What is absolutely not clear to me: does (a) mean sexual images of a 14 year old are now legal in Belgium in that case? The law does not seem to require that the owner of the pictures has to be one of the participants ... but I find it hard to believe this is the actual intent.
And to make matters even more bad, this is not the only way to punish kids. You see while this will prevent criminal prosecution, you DO NOT need a criminal conviction to lock up a minor (and they're trying to extend this). Youth services can and does, without any proof (and in practice by getting 1 social worker to say something like "it is an unhealthy relationship". They can shop around until they find one, btw, and often the one they find has never seen either kid) and in the above example lock up both partners, the younger for up to 7 years and the older up to 4. In practice they will punish the younger kid, almost always the girl.
The fun thing is when a kid is locked up for criminal reasons (bad enough so that he actually goes to prison) schooling CANNOT (and is not in practice) denied to the kid. When youth services locks kids up, they can (and are in practice) denied schooling. But of course the previous point means the police will try to use child services, not criminal prosecutions, if at all possible.
So sadly, if you want a kid's situation to improve over time and they do not want to end the relationship, your course of action is clear: you should let the abuse continue and even (help) hide it. However, if you want to hurt the kid(s) (whether or not such a relationship is actually abusive), you should report them. So here too the net result of the law is: very easy to "abuse" the law to hurt children (esp. if you are a social worker), very hard to use the law to protect children against abuse (or actually help them)