The legal basis for Manuel Noriega's arrest was a U.S. federal indictment for drug trafficking and money laundering, with the U.S. arguing the operation was a law enforcement mission to enforce these indictments, not an act of war, allowing the President to act without congressional approval. U.S. courts later upheld the conviction, establishing the precedent that unlawful capture doesn't prevent prosecution, despite Noriega's claims of head-of-state immunity, as the Department of Justice (DOJ) viewed him as a criminal, not a head of state.
When it came to clams of immunity due to being the head of state
U.S. courts dismissed Noriega's defense that he was immune as a head of state, partly because the State Department didn't recognize him as such and his alleged crimes were clearly illegal.
In short
When it came to clams of immunity due to being the head of state
https://www.ojp.gov/ncjrs/virtual-library/abstracts/dictator-drugs-and-diplomacy-indictment-head-state-immunity-united