Assange's lawyer's are likely to argue that if he is extradited to Spain, then chances are that he might be handed over to the USA where he can face execution for charges of espionage.
According to European law, suspects cannot be extradited to jurisdictions where they may face possible execution.
They will also counter the demand of extradition on the grounds that he has not been convicted for the crimes in Sweden and is only wanted for questioning which according to principles of extradition law is not a viable ground.
Assange is the founder of WikiLeaks which publishes submissions of private, secret, and classified media from anonymous news sources and news leaks.
The continous flow of US diplomatic cables being released by WikiLeaks has enraged the United States and other national governments.