The special counsel believed it had the authority to subpoena President Trump, but decided against doing so because it would delay the investigation, according to the report. The prosecutors also believed they already had a substantial amount of evidence.
“We made the decision in view of the substantial delay that such an investigative step would likely produce at a late stage in our investigation” special counsel wrote in the report. “We had sufficient evidence to understand relevant events and to make certain assessments without the President’s testimony.”
The report also says that while the Office of Legal Council opinion concludes that a sitting president may not be prosecuted, “It recognizes that a criminal investigation during a President’s term is permissible.”
The OLC opinion “also recognizes that a President does not have immunity after he leaves office,” the report says.