But Mr Barr knows that the transformation of Canberra into that rainbow city will not be without incident or diversion - which might be why he couched his remarks slightly by saying it marked ''an important step''. The federal government has already flagged its intention to challenge the bill in the High Court on the basis of advice that the bill is inconsistent with the provisions of the Commonwealth Marriage Act.

A High Court injunction preventing the ACT law from coming into operation also seems probable. Indeed, such is the federal government's determination to maintain a uniform approach to marriage throughout the Commonwealth that an attempt might also be made to have Federal Parliament override the ACT law.

So well telegraphed was the newly elected Coalition government's response to the ACT's same-sex marriage bill - and so esoteric the constitutional law that governs relations between the states, territories and the Commonwealth - that ACT Attorney-General Simon Corbell might have been expected to take all steps to make sure it was watertight.

Indeed, as recently as Sunday, Mr Corbell was arguing that amendments were unnecessary, though by Monday he'd conceded the advisability of revisions.

Whether this rushed approach proves to be the bill's salvation or its undoing remains to be seen, but in the event that it is found to be invalid, questions may be raised about the government's haste to do legal battle with the Commonwealth.

That the Gallagher government announced it intended to legislate for same-sex marriage a week after Tony Abbott's election win (knowing full well Mr Abbott's opposition to the concept) will inevitably lead to conclusions that it was intent on making a political rather than a social statement.

The ACT government can claim legitimately that its position on same-sex marriage - having been taken to the 2012 election - ought have been well known to Mr Abbott and that it had every right to act on that mandate for change. However, with at least two other states about to consider their own marriage equality bills, the ACT government might have profited by staying its hand and learning from the experiences of other jurisdictions.

It is doubtful, however, that even this prudent or sensible approach would have won the backing of the Canberra Liberals. Party leader Jeremy Hanson has continued to assert - on the rather spurious basis that he did not think ''a majority of one person in the ACT should change the definition of marriage for a country of over 23 million people'' - that the issue ''belongs in the Commonwealth Parliament''.

The logic of why Canberrans should give up the right to have laws made on their behalf (or to drive the national agenda) simply because Labor has only a one-seat majority in the Assembly may not be immediately obvious to all. Indeed, such fallacious thinking tends to suggest the Liberals are far happier dwelling on extraneous legal and political issues than in actually confronting the desirability of marriage equality laws.

Likewise, there are strong suggestions the federal Coalition's chief aim in challenging the ACT's bill is to divert attention away from the need for a debate in Parliament about marriage equality. Notwithstanding the fact that the Commonwealth has primary responsibility for marriage laws - and that opposition to same-sex marriage is still significant in certain quarters - support for change is growing. Much of it stems from the belief that all Australians deserve equality and dignity.

It is to the Gallagher government's credit that has been the first to give give official effect to that sentiment.