Mr Louis is at the centre of a storm after he showed photographs of the post mortem of Julie and Melissa, two of Belgium's most famous missing and murdered children at a news conference last week.
The Interior Minister, Joëlle Milquet (Francophone Christian democrat), asked the judicial authorities to intervene.
A dozen police officers accompanied the examining magistrate during the search of the maverick MP's home and offices. The headquarters of Mr Louis' libertarian MLD party were also raided.
As a legislator Mr Louis enjoys parliamentary immunity but this did not prevent the house searches that proceeded in the presence of the Speaker of the Chamber of Representatives.