A grand jury’s subpoena can be frustrated by an appeal to a Judge. There is a process where a subpoena can be appealed if it violates other established legal rules (like attorney / client privilege) or if it is unreasonable (produce 100,000 pages in two days). I suspect that Obama would want to claim that the grand jury does not have the authority, is not the venue to resolve, etc. Not sure if that would work as it all depends on the judge.
Then I am not at all hopeful.