“Novel and unprecedented” was Friday’s White House reaction to a unanimous appeals court decision invalidating four of President Barack Obama’s controversial “recess” appointments last year.

The same might be said even more pointedly about the plainly unconstitutional tactic used by Mr. Obama to get his way on those appointments — three to the National Labor Relations Board and one to the Consumer Financial Protection Bureau.

The Constitution gives the president power to make time-limited appointments when the Senate is in recess and cannot give its advice and consent. But it also gives the Congress power to designate when it is in recess and when it is not.

President Obama simply ignored the Senate’s declaration that it was in session when he made the controversial appointments. Saying, in effect, “Who needs a legislature?” he dismissed the Constitution’s requirement that he obtain Senate approval.

In doing so he brought on lawsuits joined by Senate and House Republicans. A sweeping decision by the federal appeals court for the District of Columbia last week not only declared the president’s four appointments invalid, it swept away more than a century of precedent that allowed recess appointments to be made during such brief interludes as national holidays.

The result, sure to be appealed to the Supreme Court, presumably wipes out a year’s decisions by the NLRB and raises questions about the legitimacy of regulations formulated by the new Consumer Financial Protection Bureau. It also sharply limits a presidential power increasingly taken for granted as a way to bypass the Senate.

A three-judge panel of the D.C. Appeals Court cast a critical eye on the Constitution and came to the conclusion that recess appointments can only be made between the annual sessions of Congress after formal adjournment.

Furthermore, said the court, the president could only fill vacancies that occurred during this formal recess.

Presidents before Mr. Obama made increasing use of recess appointments that would not be permitted under the new ruling. But he alone has taken it on himself to challenge the Senate’s right to say when it is in session, declaring a series of “pro forma” Senate sessions a sham.

The president’s supporters have accused Senate Republicans of using “trickery,” “chicanery” and “false legislative sessions” to prevent Mr. Obama from filling positions at the NLRB and elsewhere. But the “pro forma” sessions were an invention of Majority Leader Harry Reid, who used them in 2007 and 2008 to frustrate President George W. Bush.

Using pro forma sessions to block recess appointments may well be an example of hyper-partisan tactics.

But it is within the rules of Congress. The president does not have the power to declare it invalid. Meanwhile, a long assumed executive power has been sharply curbed.

The appeals court ruling curbs an unwarranted expansion of executive power.