It shall be unlawful for any person subject to this subchapter to violate any prohibition of, requirement of, or regulation promulgated pursuant to this subchapter shall be a violation of this chapter. In addition to the other requirements and prohibitions provided for in this subchapter, the operation of any affected unit to emit sulfur dioxide in excess of allowances held for such unit shall be deemed a violation, with each ton emitted in excess of allowances held constituting a separate violation.1