Constitutional lawyer George Williams says the government’s controversial plan to strip terrorists of their Australian citizenship will likely be struck down by the High Court.

Professor Williams said the legislation contained a number of measures which could face legal challenge.

It bypasses the courts, denies voting rights and goes beyond the existing “alien” powers, turning an Australian-born person into an alien because he/she has a second nationality through parents or grand-parents.

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“This bill more likely than not would be struck down by the High Court,” he told the parliamentary committee on intelligence and security that is examining the bill.

The Australian Citizenship Amendment (Allegiance to Australia) Bill 2015 extends provisions of the Citizenship Act, which strips citizenship from someone who fights for a foreign army against Australia, to include convicted terrorists and others who engaged in terror-related conduct.

Constitutional lawyer George Williams. Photo: Twitter

This would apply only to dual nationals, though that could include people born in Australia who had never lived elsewhere.

The committee is examining whether the bill should apply retrospectively, allowing convicted terrorists to be deported.

The Law Council of Australia also said it had serious concerns.

Citizenship could be lost for conduct which could be minor or unrelated to lack of allegiance to Australia.

There were inadequate safeguards and protections for children.

As well, it did not prevent indefinite detention or statelessness.

Law Council president Duncan McConnel said the mechanism for revocation was clumsy.

“The conduct or behaviour that leads to automatic loss of citizenship is very broad and imprecise. It means it would be very hard to know if someone has done something to trigger loss of citizenship until they get the notice from the minister,” he said in a statement.