First instance body dealing with electoral disputes

Loi électorale du 18 février 2003 (consolidated 17 February 2011)
19 February 2002

Art 135

Si l’éligibilité d’un candidat paraît douteuse au vu des condamnations encourues, le président du bureau principal de la circonscription fait vérifier d’urgence par le Parquet si les conditions d’éligibilité sont remplies. 

If the eligibility of a candidate seems doubtful, the president of the district's main office may urgently check if the eligibility requirements are met. 

http://www.legilux.public.lu/leg/a/archives/2011/0031/a031.pdf

In the case of Luxembourg, the electoral laws does not allow any challenges related to political party or candidate nomination and/or registration (see source: chapter III – Des candidatures [on candidatures], and its articles 135 to 139).

All candidate registrations are appreciated by the district administrative president’ main office that validates or rejects the candidacies on the bases of its harmony with the requirements established by law. In the case of rejection of a candidacy, to the rejected candidate it is given the possibility to argument against his/her rejection, claim for a revision of the process and present the necessary documents to validate his/hers candidacy.