The late Antonin Scalia famously argued in a 1989 Harvard Law School lecture that the rule of law required a "law of rules." By this he meant that judges should issue clear, specific commands — rules — to those bound by their decisions.
As Justice Scalia knew, not all laws are in fact rules. Some laws are standards. In contrast to rules, which dictate with exactitude how the law works, standards give discretion to a decision-maker to exercise his or her best judgment in the moment. "Do not consider race in college admissions" is a rule. "Treat all applicants equally" is a standard. The president cannot be younger than 35 (a rule) and, once elected, he or she must take care that the law is faithfully executed (a standard).
Rules are designed to ensure that the law is transparent and predictable, even if it means some unjust outcomes will result. Standards are designed to ensure fairness and respect for the values the law means to promote, even if it means that what the law requires at any given moment may be unclear. The rule-standard distinction matters in constitutional law not least because the framers included both in that document: Constitutionality requires that both be observed.
The distinction can help us think through the legality of Senate Republicans' refusal to fill the vacancy left by Scalia's death.
Democrats have argued that the Constitution clearly compels senators to give their advice and consent whenever the president nominates a Supreme Court justice. Republicans have argued that the Constitution gives senators full discretion to refuse to assess or vote on a Supreme Court nominee. In reality, the Constitution does neither. Both sides are acting as if advice and consent is a rule, but it is instead a standard. The constitutional text issues no straightforward command that specifies how advice and consent works, only that the Senate must play a role in appointing Supreme Court justices.
So how can we judge if the advice and consent standard is being followed? In general, we figure out how to apply standards by looking to past practice, exercising practical wisdom and observing the judgment of history. In this case, neither past practices nor practical wisdom is on the Republicans' side.
The Senate has never refused to consider the Supreme Court nominee of a popularly elected president. It has never refused consideration of a Supreme Court nominee of any president since the 19th century.
Nearly every time it has refused, the president was a former vice president — John Tyler, Millard Fillmore, Andrew Johnson — who had succeeded a deceased president. In both of the other cases, those of John Quincy Adams and Rutherford B. Hayes, the president won election through the House of Representatives after failing to achieve either an Electoral College or a popular majority. Additionally, both Adams and Hayes made their nominations in the true lame duck period, after the election but before the inauguration of a new president.
By contrast, President Obama isn't filling in for a popularly elected president; he was put into office twice by significant margins. And his nomination of Merrick Garland came more than 10 months before the end of his term.
As far as practical wisdom goes, the line the Republicans are threatening to cross will surely prompt recrimination. It's a good bet that the next Republican president facing a Democratic Senate will get an even longer stonewall than Garland seems destined to receive. Political parties do not disarm unilaterally. We are hurtling toward a future in which the president no longer gets to appoint Supreme Court justices when the opposition controls the Senate.
And what about the judgment of history? No judge will decide whether the Republicans' conduct is unconstitutional. A federal court would almost certainly regard this controversy as raising what is called a "political question," one that is beyond the judicial power to decide. But the law does not require a judicial remedy for every legal wrong any more than it requires a rule to declare a legal wrong in the first place.
We the people must be the judges in this case, and it will take time. In part, our actions will determine the outcome. Will political pressure force a hearing and a vote? Will Republicans lose their Senate majority in November? Will the confirmation process descend into pure dysfunction?
If the answer to any of those questions is yes, we will know that what past practice and practical wisdom indicate is correct: the Republicans' actions were unconstitutional.
Jamal Greene is vice dean and a professor of law at Columbia Law School.