This whole question concerning Sheriff Joe's investigation is a "tempest in a teapot", "much ado about nothing".
About 70AD some of the Sanhedrin were all nutsy concerning some men who were preaching the new faith called Christianity. An extrordinarily wise old Rabbi named Gamaliel spoke to them and said;
" Therefore, in the present case I advise you: Leave these men alone! Let them go! For if their purpose or activity is of human origin, it will fail. But if it is from God, you will not be able to stop these men; you will only find yourselves fighting against God. (Acts 5:38,39)
If you don't think Sheriff Joe has a case..leave him alone..it will come to nought; and he will have wasted his time and money.
......On the other hand, if Obama's backers think he's really onto something..they may be bothered.
As far as any 'statute of limitations'...in a case where the possibility of a person fraudently assuming office of POTUS, there should be no limitation to his/her exposure to severe penalty, nor for any who facilitated the fraud.
Note to Crusty.. Your subject title..I see you have what appears to be a typographical error in the use of "clause". I am not trying to claim anything other than a typographical error...the kind I have long suggested we ignore, let's do so.. Fair play ?