The right to practice before the IRS is regulated by Federal statute, and persons authorized to practice are known as "Federally Authorized Tax Practitioners” or FATPs. The United States Treasury grants FATP status to attorneys, CPAs, and Enrolled Agents (and to persons in a few other categories).
To become an Enrolled Agent, an applicant must pass the Special Enrollment Examination or present evidence of qualifying experience as an IRS employee. The Treasury conducts a background check of every applicant, which includes a review of the applicant’s tax compliance.