The parents of two 17-year-olds, Joe Lawton and Edward Thornber, who killed themselves after getting into trouble with police, were also at the court for the ruling.
Joe's parents, Nick and Jane Lawton, from Disley, Cheshire, say that their son would "still be here today" if he had received their support when he was taken into custody for drink driving.
We are obviously very pleased with the ruling. We knew right from the first moment that if we had been there it could have all been very different.
We are so pleased, but it is also tinged with such sadness and devastation.
Edward's mother Ann Thornber, from Manchester, also holding a photograph of her son, said:
It's just so difficult. Obviously we are delighted that some good has come out of it, but it's not going to bring Joe or Edward back.
If it can stop another family going through the devastation we have been through, there has to be something positive.
The tragedy is that Edward and Joe would still be here today if the law had been changed in 2010 but it never happened and now we are suffering the consequences of that.
More top news
A remarkably mild night with misty low cloud on the hills of Scotland, Wales and north-west England and further rain in places.
There's a wider purpose to Prince Charles' nine-day visit to Romania, Italy, Austria today.
A man and a woman, both in their early 20s, have been arrested in Birmingham on suspicion of terrorism offences.