第十七条（当事者能力及び手続行為能力の原則等）
Article 17Principles for Capacity to Be a Party and Capacity to Participate in Proceedings
With regard to a person's capacity to be a party, the capacity to perform acts in the proceedings of domestic relations cases (hereinafter referred to as "procedural acts") (hereinafter referred to as the "capacity to participate in proceedings" in this paragraph), the legal representation of a person without the capacity to participate in proceedings, and the delegation of powers as necessary for performing procedural acts, the provisions of Article 28, Article 29, Article 31, Article 33, and Article 34, paragraphs (1) and (2) of the Code of Civil Procedure apply mutatis mutandis.
In order for a person under curatorship, a person under assistance (limited to a person who is required to obtain consent from the person's assistant to participate in proceedings; the same applies in the following paragraph) or a guardian or any other legal representatives to perform any procedural acts with regard to a petition for adjudication of domestic relations or mediation of domestic relations or an appeal filed by a person other than the person, the person must not be required to obtain consent or otherwise have powers delegated to the person from the curator or supervisor of the curator, assistant or supervisor of the assistant, or supervisor of the guardian. The same applies when proceedings are commenced by the court's own authority.
In order for a person under curatorship, a person under assistance or a guardian or any other legal representative to perform any of the following procedural acts, the person must have powers specially delegated to the person:provided, however, that this does not apply where the person has obtained consent or otherwise had powers delegated to the person to file a petition for mediation of domestic relations or conduct other proceedings for mediation of domestic relations, and the person performs the procedural acts set forth in item (ii):
withdrawal of a petition for adjudication of domestic relations or mediation of domestic relations;
家事審判又は家事調停の申立ての取下げ
making of an agreement under Article 268, paragraph (1) or Article 277, paragraph (1), item (i), acceptance of the proposed terms of mediation prescribed in Article 270, paragraph (1), or filing of a joint notification under Article 286, paragraph (8); and
第二百六十八条第一項若しくは第二百七十七条第一項第一号の合意、第二百七十条第一項に規定する調停条項案の受諾又は第二百八十六条第八項の共同の申出
withdrawal of an immediate appeal against a ruling, an appeal against a ruling under Article 94, paragraph (1) (including the cases where applied mutatis mutandis pursuant to Article 288) or a petition under Article 97, paragraph (2) (including the cases where applied mutatis mutandis pursuant to Article 288), or withdrawal of an objection under Article 279, paragraph (1) or Article 286, paragraph (1).
審判に対する即時抗告、第九十四条第一項（第二百八十八条において準用する場合を含む。）の抗告若しくは第九十七条第二項（第二百八十八条において準用する場合を含む。）の申立ての取下げ又は第二百七十九条第一項若しくは第二百八十六条第一項の異議の取下げ
略称規定第一条第一項
家事審判及び家事調停に関する事件（以下「家事事件」という。）の手続については、他の法令に定めるもののほか、この法律の定めるところによる。
略称規定第十七条第一項
当事者能力、家事事件の手続における手続上の行為（以下「手続行為」という。）をすることができる能力（以下この項において「手続行為能力」という。）、手続行為能力を欠く者の法定代理及び手続行為をするのに必要な授権については、民事訴訟法第二十八条…
わかりやすく言うと
家事事件の手続の中で行われる、手続上の行為のことです。手続行為をする能力や、そのために必要な授権などについては、民事訴訟法の規定が準用されます（第十七条第一項）。
略称規定第十七条第一項・この項の中だけ
当事者能力、家事事件の手続における手続上の行為（以下「手続行為」という。）をすることができる能力（以下この項において「手続行為能力」という。）、手続行為能力を欠く者の法定代理及び手続行為をするのに必要な授権については、民事訴訟法第二十八条…
わかりやすく言うと
家事事件の手続で手続行為をすることができる能力のことです。この能力には民事訴訟法第二十八条などが準用され、原則として民法その他の法令に従って決まります（第十七条第一項）。