Senator Marsha Blackburn of Tennessee has filed a lawsuit challenging a subpoena issued by special counsel Jack Smith.
The subpoena relates to Smith’s ongoing inquiry into former President Donald Trump.
Blackburn’s suit tests the scope of the Constitution’s “speech or debate” clause.
That clause shields lawmakers from legal action tied to their legislative duties.
Smith’s subpoena sought information from Blackburn as part of his investigation.
The lawsuit argues the subpoena oversteps constitutional protections for members of Congress.
It asks a federal court to block the subpoena and declare the request invalid.
The case could set a precedent for how far prosecutors may go in probing lawmakers.
Smith’s inquiry has already produced subpoenas for other officials and aides.
Blackburn has publicly criticized the special counsel’s investigation into Trump.
Legal experts say the dispute may reach higher courts due to its constitutional stakes.
A ruling could clarify the boundaries between congressional immunity and criminal probes.
No hearing date has been scheduled yet for the lawsuit.
