While most (not all) USCIS denials do not require an administrative appeal in order to proceed to federal district court to fight the denial, Naturalization (N-400) denials are different. Once USCIS denies a naturalization application, a lawsuit can be filed under 8 USC §1421(c). However, before seeking judicial review, the administrative appeal process should be completed by requesting a hearing under §1447(a) through the submission of a form N-336.