Private investigations are illegal WHILE AN OFFICIAL POLICE INVESTIGATION IS TAKING PLACE, they are not illegal per se.
Very much so and the status quo back in 2007 was very different to what it is now in 2014. Private criminal investigators would not be tolerated in the UK in a live investigation so I fail to see how Portugal is any different unless of course it is considered the 'wild west' by the ill-informed and those with an agenda to pursue.
It all comes down to interference with an official investigation which can be rightly labelled obstruction or attempting to pervert the course of justice. In her book, Kate McCann states that the reason for using Método 3 was because the PJ were no longer searching for Madeleine. That was in fact a false assessment of the situation. Senior PJ officers gave evidence at the recent hearings in Lisbon that the case was never closed even after the archiving. Even then, a small team was tasked with disseminating any new information which came into them about the case. The search for Madeleine never ended.