The US Supreme Court on Monday announced its first ethics code after judges on the nation's top court faced mounting criticism over financial contributions and luxury trips.
The nine justices on the Supreme Court have long acted without a formal ethics code, unlike others on the federal judiciary.
Justice Clarence Thomas was at the centre of a report by ProPublica this year, which alleged he had accepted luxury trips from Republican donor Harlan Crow.
The report found that Mr Thomas had accompanied Mr Crow on his private jet and superyacht.
But other judges have also received scrutiny.
A separate report from ProPublica alleged that Justice Samuel Alito had gone on holidays with a Republican billionaire who had cases before the Supreme Court.
Justice Sonia Sotomayor's office pressured universities and libraries to buy her books, AP reported.
In an unsigned statement, the nine justices said they had adhered to ethical standards.
“The absence of a code, however, has led in recent years to the misunderstanding that the justices of this court, unlike all other jurists in this country, regard themselves as unrestricted by any ethics rules,” they said in a statement.
The justices said the formal ethics code represents principles that they have “long regarded as governing our conduct”.
US Senate Democrats have pushed for the Supreme Court to instil an ethics code.
Senate judiciary committee chairman Dick Durbin last week also announced that the panel would vote on issuing subpoenas relating to the committee's investigation into the Supreme Court's ethics.
“Over the last several months, it’s become clear that the Supreme Court is in desperate need of a binding code of ethics as we learn of lavish gifts and luxury travel that certain Supreme Court justices have accepted from a gaggle of fawning billionaires,” Mr Durbin said.
Americans' views on the Supreme Court are fading. Only 49 per cent trust the institution, near a historic 47 per cent low, according to a Gallup poll released before the court began its term in September.
Only 41 per cent of Americans approve of the Supreme Court's job performance, which is also near a record low of 40 per cent.