States defending their discriminatory marriage laws before the Supreme Court insist that it is up to their voters or legislatures to decide whether loving, committed same-sex couples will have the right to marry, and that courts have no business interfering with the result. That’s not how our Constitution works.

Liberty, dignity and equality for all are not policy preferences to be weighed by voters or their elected representatives. They are constitutional mandates written in the text of the 14th Amendment. There is no “will of the majority” exception to the Constitution.

Indeed, the story of our Constitution, in large measure, is a story of the need to curb majorities in the states in order to protect our deepest constitutional values of liberty and equality for all. From the founding on, preventing tyranny of the majority at the state level has been a consistent theme of our Constitution.

Worried by legislative excesses in the states, the framers wrote into the Constitution a number of specific limits on state governments to ensure, in the words of James Madison, that the majority would be “unable to concert and carry into effect schemes of oppression.” The most important of these was the Supremacy Clause, which declared the Constitution the “supreme law of the land” which all states must respect. As the Supremacy Clause makes clear, the people of a state cannot use the democratic process to adopt state constitutional provisions or state laws that transgress the U.S. Constitution. Whatever a state does must respect the higher law set out in the federal Constitution.

The original Constitution turned a blind eye to slavery, but nearly 70 years after the adoption of the Constitution, in the wake of a bloody civil war, the American people amended our founding charter to add new restrictions on state governments and redeem the Constitution from the sin of slavery. The 14th Amendment’s sweeping guarantees protect fundamental rights and outlaw discrimination against all people, whether black or white, man or woman, or straight or gay, preventing legislative or popular majorities from oppressing minorities. Under the 14th Amendment, states cannot treat any group of individuals as inferior, second-class people or deny them core aspects of liberty.

No one doubts the vibrant and essential role that states play in our system of federalism or the importance of democratic deliberation by the people on the issues of the day, but under our nation’s charter, constitutional guarantees are not subject to a vote. Where the Constitution kicks in, state authority must give way. Thus, as the Supreme Court has held many times, the government cannot use the democratic process to write inequality into the law. That’s the principle the Supreme Court vindicated in Loving v. Virginia, when it overturned state laws that prohibited interracial marriage. It is also at the heart of the 2013 decision striking down a key provision of the Defense of Marriage Act. The same reasoning should lead the justices to strike down discriminatory marriage laws that prohibit same-sex marriage.

The 14th Amendment does not permit the voters of a state to impose a badge of inferiority on committed same-sex couples and their families and deny them the right to marry. When the justices hear oral arguments this week, they should remember that the will of the people can’t trump the basic guarantees of personal, individual rights set out in the text of the Constitution. It is the Supreme Court’s job to enforce the Constitution’s guarantee of equality for all.