Both HCI and referrenda are listed as methods of affecting the DOP, so I'd assume they'd both be excepted, still a tad confused by state referrals
All three methods of changing the division of law making powers are valid answers.
- High Court Interpretation can take what has previously been thought to be a residual power and change it to a concurrent power. See Brislan for a great example of wireless radio moving from residual to concurrent.
- Referendums, also can change residual to concurrent. See the 1967 referendum whereby the power to make laws regarding Aboriginal people was residual and also a restriction on the Commonwealth until the referendum removed the restriction allowing the Commonwealth to move it this area (states were not excluded) thus a concurrent power.
- Referral of powers can be argued to change a residual power to concurrent. It is correct to say the power is given to the Commonwealth but as yet we are unsure if this makes the power exclusive or concurrent. I would argue it is concurrent. However, until a test case occurs whereby there is an inconsistency in an area of referred power we just don't know what the actual affect of referral is. So that is also an acceptable answer.
I believe the assessors will take all three as acceptable.