The Environmental Protection Agency (EPA) is finalizing a limited approval and limited disapproval of a revision to the Mojave Desert Air Quality Management District's (MDAQMD or District) portion of the California State Implementation Plan (SIP). This revision concerns oxides of nitrogen (NO<INF>X</INF>) emissions from stationary internal combustion engines. Under the authority of the Clean Air Act (CAA or the ``Act''), this action approves a local rule that regulates these emission sources into the federally-enforceable SIP, thereby strengthening the SIP, while identifying deficiencies with the rule that must be corrected by the MDAQMD in order for the EPA to grant full approval of the rule.