He said the case now had two layers. "Mr Dotcom is fighting for his rights and he's fighting for the rights of all New Zealand residents to be free from domestic spying."
Mr Key's acknowledgment this week that the GCSB had unlawfully spied on Mr Dotcom placed the US bid to extradite his client in jeopardy.
"If there is a certain degree of illegal conduct by the Government in the manner and method in which they go about arresting and prosecuting the case, it could get to the point where the case ought to be dismissed in the interests of justice."
Mr Rothken said his team would now press for full disclosure of the GCSB's involvement and that of any US spy agency.
"We believe they should hand over everything related to the type of domestic spying they were doing on Kim Dotcom and others in this case - not just what they gave to the police."
"Not only do we want to get disclosure of any communications between New Zealand spying authorities and the New Zealand police but we want to get communications between New Zealand spying authorities and US spying authorities if it relates to a resident of New Zealand.
Mr Rothken said his team also wanted to know whether Echelon, the US system of global electronic eavesdropping which the GCSB feeds into through its Waihopai and Tangimoana facilities, was involved.