A Senate investigation into former special counsel Jack Smith’s Arctic Frost inquiry is examining Verizon’s decision to comply with subpoenas for Republican lawmakers’ phone records. The issue matters because Republicans argue the requests may have bypassed constitutional protections for members of Congress, while Verizon says it was responding to legally valid demands.

Senator Chuck Grassley said Verizon and other carriers received subpoenas connected to the investigation that preceded Smith’s election-related case against Donald Trump. Verizon provided limited call-detail information for some lawmakers and later said it had changed its procedures to scrutinise law-enforcement requests involving Congress more closely; AT&T said it challenged similar requests and did not provide records.