Legal guardianship gives authority to a person to care for a child when the child's parents are not able to care for him. Legal guardianship is often obtained through court orders or through written wills and powers of attorney. There are various situations in which you may be required to prove legal guardianship of a child, such as for medical care or school matters. Legal guardianship laws vary from state to state, but generally, presenting the appropriate documents is the only way to determine that you are the child's legal guardian.

Obtain letters of authority or letters of guardianship from a judge by filing a petition for guardianship with your probate court. Obtain the petition forms from the court clerk and fill them in. Attend the hearing date and receive the letters of authority or letters of guardianship from the court if your petition is successful.

Acquire power of attorney from the person (usually the parent) who is granting you legal guardianship of the child. Power of attorney is a legal document that allows the legal guardian to take care of personal and business matters on behalf of a parent. Present this to court to obtain letters of guardianship.

Receive a copy of the will in which you are named as the legal guardian by the child's parents. Obtain a written letter of explanation from the parent that indicates the reasons why the parent has chosen you to be the guardian. Present these in court or in any situation that requires you to prove legal guardianship.

Keep copies of update reports about the child's health, hobbies and place of residence. These reports are written annually by the guardian and submitted to the court. Present these update reports together with the above legal documents as proof of legal guardianship of a child.