by the United States government

“ In order to insure electric reliability, such regulations shall not prohibit or affect temporary increases and decreases in emissions within utility systems, power pools, or utilities entering into allowance pool agreements, that result from their operations, including emergencies and central dispatch, and such temporary emissions increases and decreases shall not require transfer of allowances among units nor shall it require recordation. ”

“ It shall be unlawful for any affected unit to emit sulfur dioxide in excess of the number of allowances held for that unit for that year by the owner or operator of the unit. Upon the allocation of allowances under this subchapter, the prohibition contained in the preceding sentence shall supersede any other emission limitation applicable under this subchapter to the units for which such allowances are allocated. Allowances may not be used prior to the calendar year for which they are allocated. ”

“ Interpollutant trading Not later than January 1, 1994, the Administrator shall furnish to the Congress a study evaluating the environmental and economic consequences of amending this subchapter to permit trading sulfur dioxide allowances for nitrogen oxides allowances. ”