Absolutely right. Mandates are all very well, whether within universities or nationally, but they are worthless unless they are complied with. Penalties for non-compliance are effectively impossible. I heard someone at UKCoRR compare the situation to speeding fines lately. Do these stop people from driving at 40mph in a 30mph zone? No. In fact, the fact that the law is unenforceable, penalties not withstanding, tends to bring any law or mandate into disrepute.
Two things will make OA work: (1) active and continuous advocacy; (2) mandates from funding bodies, with future funding conditional on compliance. However, we have already encountered academics under such financially dependent mandates who did not realise this, and without advocacy on our part would apparently have been penalised in future. All this simply shows that the carrot is always more effective than the stick. This should be obvious to anyone who has been involved in education. You can, as the saying goes, take a horse to water, but you can't make it drink. Brussels will have to deal with OA when the time is ripe. Cheers, Talat