How can you prove anything against them? Hafeez is in Pakistan and ISI is an organisation which you can't bring to India. Even Hafeez will not know who actually ordered him to do it.
Atleast cant we pin attempts of conspiracy, sabotage, etc against congress, by doing full investigation into the home ministry and defence ministry. By taking statements of the officials. And pinning on who manipulated the location intelligence from inside. That is for a start. We can take statements from Army heads that Col,Purohit was an excellent officer and that he was framed. Statements from Purohit and his investigation details where he found out about the Samajwadi Party mole. All these. All we have to do is put some doubt into the public. Doesn't need proving if thatis touch. And given the gains made if it is ever proved, it will be worth sending a team into Pakistan and picking up Hafeez Said and his handlers somehow (RAW can do it no?). I mean the way you decide is something is worth taking action on is by chekcing the gains made from doing it. In this case, if we can prove to public any congress role in 26/11 and attempts to defame Hindus, then that itself will destroy them. Totally worth it.