The hearing for the petition, which was filed by The Heritage Foundation's Oversight Project, was open to the press.
The organization is seeking information from government authorities to determine whether the Duke of Sussex received preferential treatment from the US government.
This hearing coincided with Prince Harry's presence in the United Kingdom, where he was set to testify before the High Court in London in his case against a newspaper group.
It remains uncertain whether the Duke of Sussex would be represented by his lawyers in the US.
The conservative group claimed that Prince Harry admitted in his book, "Spare," to being a frequent drug user. In their complaint, the organization highlighted that according to "US immigration law, individuals who admit to a drug crime are prohibited from entry. They can only enter temporarily if they obtain a waiver."
Meanwhile, the Duke of Sussex arrived at London's High Court on Tuesday to provide evidence in his lawsuit against the publisher of the British tabloid, the Daily Mirror. He accuses them of engaging in phone hacking and other illegal activities.
Although he failed to appear in court as expected on Monday, he took the stand on Tuesday.
MGN, now owned by Reach (RCH.L), apologized at the beginning of the trial for one instance where the Sunday People unlawfully sought information about Prince Harry, acknowledging his entitlement to compensation.
