Attorney-General George Brandis has refused to guarantee that proposed laws to strip citizenship from dual national terror suspects could withstand a High Court challenge.
Crossbench senators have probed Senator Brandis over the constitutionality of the legislation in the Senate, with Independent senator Jacquie Lambie calling for his resignation if the laws are successfully challenged.
Senator Brandis insisted the government had been informed by the best legal advice available "that the legislation is as strong as we can make it from a constitutional point of view".
But there are no guarantees.
"Nobody should make hard and fast predictions about what may be decided by the High Court and I don't intend to do so," he said.
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Greens and crossbench senators fear the legislation will make Australians more vulnerable to terrorist attacks.
Greens leader Richard Di Natale said the measures amounted to "exporting" terrorists, allowing criminals with a grudge towards Australia to roam the world instead of being locked up in secure Australian jails.
Independent senator Nick Xenophon said it could make Australians holidaying or living overseas terrorist targets.
The controversial legislation is expected to pass the upper house by the end of the week, with the support of the opposition.
