The high court said, however, that Trump could challenge the subpoena on other grounds.

That investigatory effort is on hold while Trump's lawyers challenge the subpoena in court.

He would then be able to challenge the subpoena in court if he did not want to give evidence.

Google provided Port with notice of the subpoena, giving the blogger an opportunity to anonymously challenge the subpoena in court.

Harris' lawyer, Martin Stolar, said he was disappointed that Twitter had handed over the messages but vowed to continue to challenge the subpoena.

Without notice, "there's no one in the picture that's ready to challenge the subpoena and bring it before a judge," he said.

The ruling, written by Chief Justice John Roberts, said Trump can challenge the subpoena as an attempt to influence the performance of his official duties.

Twitter and Harris had challenged the subpoena but Sciarrino rejected their arguments in June.