This is because statutes must be interpreted consistently with international law insofar as the text permits. See explanation in Plaintiff M70/2011 v Minister for Immigration & Citizenship [2011] HCA 32; (2011) 244 CLR 144; (2011) 85 ALJR 891; (2011) 280 ALR 18; (2011) 122 ALD 237 at [54] per French CJ, [94]-[98] per Gummow, Hayne, Crennan and Bell JJ and [239] per Kiefel J, and Minister for Immigration & Citizenship v SZQRB [2013] FCAFC 33; (2013) 210 FCR 505; (2013) 296 ALR 525; (2013) 132 ALD 269 at [229]-[231] per Lander and Gordon JJ and [313] per Besanko and Jagot JJ.
The limitation on the removal power in section 198, identified in Plaintiff M70, was sought to be overturned by the introduction of section 197C. See discussion in WZAWB v Minister for Immigration [2016] FCCA 1345; 309 FLR 398 at [171]-[192]. The effect of section 197C does not otherwise appear to have been considered.