Aside from the political tit for tat that will be bound to happen if former presidents are paraded through the courts, it can be argued that, like cops, judges and prosecuters, presidents and officers of the United States have immunity for actions taken during the performance of their duties. And if they do not it will take years for the courts to settle the question, further destroying the public's faith in their governing institutions. 

The time to nip the problem is while the president and officers are available for impeachment.