In a joint statement the five NSW Parliamentarians have welcomed a Tasmanian Law Reform Institute Report into state based same-sex marriage saying:  

"The findings of the Tasmanian Law Reform Institute Report add further credibility to a the recent NSW Parliamentary Inquiry that found a State can legislate for same-sex marriage"

"Based on the solid legal and constitutional advice available, we continue to be confident that States can progress with a reform that has wide-spread support and will benefit couples, families, and communities" 

"If there is a high-court challenge to legislation, both reports give us confidence that NSW Same-Sex Marriage laws would survive any such  challenge"

The report also found that historically in Australia relationships are  recognised first a state level and then later at a federal level and  that a referendum could not resolve the issue of same-sex marriage.

The Tasmanian Law Reform Institute can be found below:

http://www.utas.edu.au/__data/assets/pdf_file/0004/424525/SSM_FinalB5_05.pdf