the united states supreme court decided that in the united states versus nixon. and so, if you will, they can negotiate away their rights to a grand jury subpoena right up to that point. >> what limits -- i mean, assuming they would want to negotiate rather than have the president be subpoenaed, what legal limits could be imposed on how the interview is conducted, the terms of it and the scope of it? >> they really have no sort of leverage over mueller. they're at mueller's beck and call. when we did our interview in my independent counsel investigation of herbert walker bush, we were very deferential with respect to time and place so we minimally interfered with his schedule but that's all that we were willing to do and that's all that i think mueller would be willing to do.