I have it from a 'reliable source' that as it currently stands, if someone from CASA stops you on the tarmac and asks you to submit to a drug/alcohol test you are not under any obligation to do so!!
Indeed, you may even invite the person requesting you to do the test to take a long walk off a short jetty, or whatever other form of refusal tickles your fancy.
And an official from your company is in the same position,unless the provision to apply these random tests is written into your employment contract and you have signed it.
Legislation to permit CASA to undertake these tests and require a pilot to submit to the test must be passed by Federal Parliament and then, as I understand it, only those CASA officials authorised by the legislation will be permitted to carry out the testing.