International Covenant on Civil and Political Rights, Article 14.3.d

In the determination of any criminal charge against him, everyone shall be entitled, in full equality, to be tried in his presence, and to defend himself in person or through legal assistance of his own choosing; to be informed, if he does not have legal assistance, of this right; and to have legal assistance assigned to him, in any case where the interests of justice so require, and without payment by him in any such case if he does not have sufficient means to pay for it.