Why the same-sex marriage bill will end up in the High Court

There are several major constitutional questions. The first question is: Who has standing to challenge such a law? Then the question arises as to what is marriage as defined in the Constitution? And then whether the Commonwealth's existing Marriage Act leaves any room for a state or territory to enter the field.

As to standing, any number of religious groups would be happy to enter the fray, but the High Court has been fairly wary of “busy-body” interference by parties whose legal interests are not directly affected.

If we were dealing with a same-sex marriage law passed by a state, the Commonwealth could certainly launch a challenge. Whether it can challenge an ACT law might be a different question because the ACT legislature is a creature of the Commonwealth, so the Commonwealth would be challenging itself.

As things stand the Commonwealth ACT Self-Government Act requires both houses of the federal Parliament to agree before an ACT law can be annulled.

A Commonwealth High Court challenge, on the other hand, can be launched on the say so of the Federal Attorney-General. Given the change of government, this would be very likely.

Let's, for the moment, imagine the ACT is treated just like a state for this exercise. And let's face it, one or other states is likely to legislate for same-sex marriage before too long.

The Constitution gives the Commonwealth Parliament various powers, including the power “to make laws with respect to ... marriage”.

But I shall use a less contentious power to illustrate the constitutional points. The Commonwealth Parliament has power to make laws “with respect to currency”.

It has got several options: do nothing; introduce its own currency but let the states continue to have theirs; or have its own currency exclusively, prohibiting the states from having currencies.

As it happens, the Commonwealth chose the last of these, specifically excluding the states from issuing their own currencies.

But just say a naughty state sought to get around this by issuing a whole lot of promisory notes or bonds and did it electronically. People who held these bonds could use them to buy goods over the internet.

The question then becomes: Are these bonds “currency” within the meaning of the Constitution? It is for the High Court to determine the meaning of words in the Constitution. The Commonwealth Parliament could not legislate to say “currency” means any paper or electronic transaction under which a state or a person promises to pay money and force anyone who wanted to borrow money to borrow from the Commonwealth.

The High Court would strike down such as law as beyond the Commonwealth's power.

Returning to marriage, it is for the High Court to define the word. Certainly, in 1901 nobody envisaged that the word “marriage” could include a same-sex union, just as nobody could envisage electronic currency.

The High Court has grappled with the correct interpretive principle. Does it account for changes in meaning of words over time as well as account for changes in what a word's meaning might embrace? For example, the word “transport” in a 1901 Constitution would now clearly include aircraft. But should the court allow for changes in meaning so that the word “defence” includes measures against internal terrorism which in 1901 would have been considered merely crimes.

It is of Aristotelean proportions and like Aristotle, the court has had two bob each way.

It is really anyone's guess as to whether the court would say the word “marriage” includes same-sex unions. If so, the Commonwealth could legislate for them. If not, we would need a referendum to enable the Commonwealth to do so.

Either way, where does this leave the states (and the ACT)?

The easy answer is if the High Court holds that “marriage” includes same-sex unions. In that case the constitutional power would enable the Commonwealth to allow them or prohibit them and prohibit the states from allowing them – just like “currency”. A power “with respect to” something is a power to prohibit it.

Has the Commonwealth already done that with changes to the Marriage Act in the term of the Howard Government?

Possibly, possibly not.

In 2004 the Marriage Act was changed adding a definition: “ 'marriage' means the union of a man and a woman to the exclusion of all others, voluntarily entered into for life.”

The court might say that that section is invalid because it is a stream attempting to reach higher than its source – that the Commonwealth Parliament is trying to define its own powers when the Constitution says that that is the job of the High Court.

Equally, the court might say that the section is an expression of the Parliament's will to limit the application of the marriage power to different-sex marriages and to prohibit all other marriages. That is, to cover the whole field of marriage, leaving no room for state action.

In fact, the Howard Government messed it up. It was so keen on symbolism and pandering to the religious lobbies, that it might have failed in its legal purpose: to prohibit the states from legislating for same-sex marriages.

It should have said something like: “The only marriages to be recognised in Australia are those entered into by a man and a woman.”

But that wording, by specifically excluding same-sex marriages, would have implicitly have recognised that such things were at least within the realm of possibility. You have to acknowledge that something is within the realm of possibility before you can prohibit it.

Oddly enough, those in favour of same-sex marriages should hope that the High Court strikes down the ACT law on the grounds that the Commonwealth has covered the field. Only that way can there be Commonwealth same-sex marriages without a referendum. And ultimately, marriage equally can only really be achieved with a Commonwealth law, even if it will be a long time coming.

In the meantime, the states and territories will be tinkering at the edges and the Commonwealth, through executive and regulatory means, can make state and territory unions inferior, by not recognising them for a whole lot of federal rights, benefits and obligations.

My guess is that the religious lobbies might well win a few battles against state and territory laws, but will ultimately lose its battle against marriage equality nationwide.

Crispin Hull is a Canberra Times columnist.