I cannot find it at the moment, but I believe there are provisions under the transport act governing professional drivers and operators of machinery. This stipulates that any person acting as a professional driver / operator must not exceed 0.00 BAC.
Most companies have drug and alcohol policies in place whereby specific figures and penalties are noted. This would be encompassed in most operations manuals. The companies have the option of requesting a qualified testing authority, either a qualified member of the company or suitable tester with can include a member of the police.
Anyone who refuses on private land is subject to company dicipline if no legal offense occured. If an offence has been deemed commited by the appropriate authority to have occurred, then the offender is subject to the bounds of the law and the enforcers of it. This also can depend on who owns the airport. State police are often present at airports around the country for various reasons from business to trespass. (Anyone visiting Darwin airport can vouch for that!)
To use some of my miners as an example as there are similarities. They have legal and company requirements not to drive above 0.00. They have not committed an offense coming to work, as they caught the company shuttle bus, but it is deemed that given they were dressed and on the bus heading to their place of work, that they had every intention of operating the machinery. This is deemed as intent. These lads and lasses have access to BAC breathalizers 24/7. These units are subject to and are calibrated to the same standard by the same folks that calibrate police units.
As a paramedic with authorised BAC and drug testing qualifications (and plenty of time on the other end of drunken abuse!) I am permitted to test any pilot landing on specific mining leases when acting on behalf of the company. Now, that pilot can refuse a drug and/or alcohol test, but by the single act of landing on the lease he/she has subject themselves to the regulations covering that lease. While I cannot press charges, I can pass on relevant information to security and that pilot will be sent back at his or her own expense, with a ban on re-entry.
So, while you think you are safe on a fedrally owned airport, with headsets in hand, flicking mental "birds" at the officers left standing at the fence, it may not be that easy. Your future may well be in jeopardy, particularly, if you get a reputation for flying under the influence. A history of mistakes and general poor performance are key employment indicators.
And think about this... those same police may be on their nightshift, picking up the pieces of you and your attitude as you drive home fatigued that night.