Another bill — introduced by Lindsey Graham, Republican of South Carolina, and Cory Booker, Democrat of New Jersey — would go a step further. If the attorney general wanted to remove the special counsel, he would first have to seek pre-approval from a three-judge panel. The special counsel could be fired only after the panel found that the removal criteria had been met. Under both bills, the three-judge panel’s ruling could be directly appealed to the Supreme Court.

While both bills are likely to face constitutional objections, we think that they’re likely to pass judicial muster: In the 1988 case Morrison v. Olson, the Supreme Court blessed a similar removal provision in the independent counsel statute. The problem with the new bills is not that they are unconstitutional; it is that they are ineffectual. While they make it harder for Mr. Trump to fire Mr. Mueller, they still allow the president and his subordinates to obstruct the investigation in countless other ways.

The roots of Mr. Mueller’s vulnerability date back to the middle of 1999. At the time, most Democrats thought that Kenneth Starr, the independent counsel investigating various allegations against President Bill Clinton, abused his power. And many Republicans believed that the independent counsel who investigated Reagan administration officials involved in the Iran-contra affair had also gone too far. When the independent counsel statute came up for renewal, lawmakers from both parties decided to let it lapse. In its place, President Clinton’s Justice Department issued a new set of regulations allowing the attorney general to appoint a “special counsel” to investigate administration officials accused of misconduct.

Those rules put the special counsel on a short leash. They require the special counsel to notify the attorney general at least three days before any major investigative or prosecutorial step, and they authorize the attorney general to stop the special counsel from proceeding. They also require the special counsel to seek reauthorization from the attorney general every Oct. 1 in order to press forward with his inquiry, and they allow the attorney general to set the special counsel’s budget. With Attorney General Jeff Sessions recused from the Russia investigation, oversight of the special counsel falls to the deputy attorney general, Rod Rosenstein.

So if President Trump wants to halt Mr. Mueller’s inquiry, he can order Mr. Rosenstein not to reauthorize the special counsel’s investigation this October or to starve the special counsel of funds. If Mr. Trump wants to stop Mr. Mueller even sooner, he can instruct Mr. Rosenstein to exercise veto power over the special counsel at every step of the way. And if Mr. Rosenstein rebuffs the president’s commands, Mr. Trump could replace him with a loyalist who will follow his instructions. Neither bill deals with these scenarios, and yet they’re the likeliest avenues for Mr. Trump to interfere with Mr. Mueller’s work.