Berlin (dpa) - German Tornado jets prepared to fly to Turkey Thursday in support of US-led efforts to defeat the Islamic State militant group as a legal opinion commissioned by Germany‘s hard-left Die Linke party (The Left party) concluded the deployment could not be justified under international law."The legal justification relied on by the German government for the deployment of German military forces to Syria is unsustainable," said the 11-page opinion drafted by Norman Paech, a retired professor of law.The party, which holds 64 of the 631 seats in the Bundestag, the lower house of parliament, said it intended to formally present Paech‘s opinion to parliament Thursday.Paech, a former member of the Bundestag and Hamburg University professor, noted in his opinion that the Syrian state was not responsible for terrorist attacks, such as that carried out in Paris on November 13.For that reason, no airstrikes may be carried out on Syrian territory without Damascus‘ permission, he wrote.The German government is using the UN Charter, which includes "the inherent right of collective or individual self-defence" in the face of armed attack, to justify its decision to deploy 1,200 military personnel.Paech said he believes the UN Charter does not apply in this case."International law insists as always that a state can only be attacked if the terrorist attacks emanating from its territory can be attributed to it," he said.It was not immediately clear what effect the move by the Left Party would have with experts suggesting it would be difficult to challenge the decision taken by the Bundestag.The first German Tornado reconnaissance jets were leaving for Turkey on Thursday along with a tanker aircraft ahead of beginning missions against Islamic State in Syria and Iraq in January.German aircraft will not participate in bombings in terms of the mandate passed by parliament.The German frigate Augsburg is already off the Syrian coast supporting the French aircraft carrier Charles de Gaulle, from which French fighter bombers are attacking Islamic State targets.