§1. When a single judge or the president of a collegiate tribunal has seen that the matter is within his competence and the petitioner does not lack legitimate personal standing in the trial, he must accept or reject the libellus as soon as possible by decree.
§2. A libellus can be rejected only: 1/ if the judge or tribunal is incompetent; 2/ if without doubt it is evident that the petitioner lacks legitimate personal standing in the trial; 3/ if the prescripts of can. 1504, nn. 1-3 have not been observed; 4/ if it is certainly clear from the libellus itself that the petition lacks any basis and that there is no possibility that any such basis will appear through a process.
§3. If the libellus has been rejected because of defects which can be corrected, the petitioner can resubmit a new, correctly prepared libellus to the same judge.
§4. A party is always free within ten available days to make recourse with substantiating reasons against the rejection of a libellus either to the appellate tribunal or to the college if the libellus was rejected by the presiding judge; the question of the rejection is to be decided as promptly as possible (expeditissime).
Source: Code of Canon Law (Vatican.va)