Video and slides from the IPRIA seminar on trade marks and plain paper packaging of cigarettes (it's been a long day, so forgive the drollery about cancersticks) are now online.
The Mark Davison slides are strongly commended and for example note the 'Constitutional Argument' that restrictions are permissible because there has been no 'acquisition' of property - "The mere extinguishment or deprivation of rights in relation to property does not involve acquisition", as per Commonwealth v Tasmania (1983) 158 CLR 1, Mutual Pools & Staff Pty Ltd v Commonwealth (1994) 179 CLR 155, Newcrest Mining (WA) Ltd v Commonwealth (1997) 190 CLR 513 etc.