The Constitution mentions neither congressional oversight nor executive privilege. But it is now well settled that both exist. In 1927, the Supreme Court held that each house of Congress had the power “to compel a private individual to appear before it or one of its committees and give testimony needed to enable it efficiently to exercise a legislative function belonging to it under the Constitution.” And in 1974, in United States v. Nixon, the Supreme Court confirmed the existence of a constitutionally grounded executive privilege that shields, among other things, certain communications with the president. In that case, however, the court also ruled that the privilege was not absolute and did not shield Richard Nixon’s White House tape recordings from being released to the special prosecutor in the Watergate investigation.

Does this mean that Mr. Trump’s communications are fair game? It is hard to say. The case of the Nixon tapes involved a judicial subpoena issued in connection with a criminal trial, not a congressional investigation. Some have argued — as Attorney General Bill Barr did, during his previous stint as attorney general, in the George H.W. Bush administration — that executive privilege is at least as strong if not stronger against congressional demands for information.

One reason there is so little clarity on this question is that the courts have not had a chance to tell us. To a remarkable extent, the courts have been silent bystanders during the frequent disputes between Congress and the executive over access to information. That is because negotiation and accommodation have long led to the resolution of these disputes outside of the courts. A give-and-take between the two political branches of government usually results in congressional requests being narrowed but ultimately complied with. Each side scores some wins and suffers some losses, and a meaningful if limited investigation occurs.

Under ordinary circumstances, the process of accommodation would start now. But this process is grounded in informal norms, such as the expectation that the political branches will proceed in good faith and with mutual acceptance of their respective roles in our constitutional system.

The Trump White House, unfortunately, has shown little interest in respecting such norms. The prospect of a negotiated resolution thus seems unlikely. House committees, if faced with refusals from President Trump’s advisers to testify or turn over documents, are likely to issue subpoenas and seek to enforce them in court through contempt proceedings.