§1. Secular clerics have the right to associate with others to pursue purposes in keeping with the clerical state.
§2. Secular clerics are to hold in esteem especially those associations which, having statutes recognized by competent authority, foster their holiness in the exercise of the ministry through a suitable and properly approved rule of life and through fraternal assistance and which promote the unity of clerics among themselves and with their own bishop.
§3. Clerics are to refrain from establishing or participating in associations whose purpose or activity cannot be reconciled with the obligations proper to the clerical state or can prevent the diligent fulfillment of the function entrusted to them by competent ecclesiastical authority.
Source: Code of Canon Law (Vatican.va)