It was proposed last month, after a US trade investigation into forced labour.The defence minister says the US-Australia free trade agreement has been "enormously beneficial" to Australia.He's rejected concerns about Australia's modern slavery regime, which he says is one of the best legal regimes in the world."We share an objective there to stamp that out There's a balance here which has to be struck."Defence Minister Richard Marles has defended Australia's modern slavery laws after the US said it would slap 12.5 per cent tariffs on Australia.The tariff was proposed last month, after a US trade investigation into forced labour.As we've reported, the US trade representative has now announced the proposed tariff will take effect from 2:01pm Friday AEST.Speaking to ABC Radio National Breakfast, Marles says the US's decision "makes no sense", and the government is disappointed by the decision."This really, in our view, makes no sense