Unfortunately the relevant prosecutor will simply decline to prosecute. We didn't always have this loophole. The original purpose of grand juries was to allow

Unfortunately the relevant prosecutor will simply decline to prosecute. We didn't always have this loophole. The original purpose of grand juries was to allow any citizen to bring criminal charges, so that political appointees wouldn't have this "pre-conviction pardon" capability. The grand jury's job, when returning an indictment, was to appoint an attorney general for that particular indictment: https://en.wikipedia.org/wiki/Grand_jury#United_States https://en.wikipedia.org/wiki/Grand_jury#United_States