Today we celebrate the birthday of the great Martin Luther King, Jr., whose life and career demonstrate the enduring importance of our constitutional ideals and the centrality of the courts in making them a reality. Compared to contemporaries like Thurgood Marshall, King is often recognized for his social activism rather than pursuing change through strategic litigation. But King described himself as a “notorious litigant” and a “frequenter of jails,” and his fight for freedom and equality demonstrates the interplay between social change and constitutional law.

King revered the Declaration of Independence and the Constitution—calling them “a promissory note to which every American was to fall heir.” Of the Declaration, he said, “[n]ever before in the history of the world has a sociopolitical document expressed in such profound, eloquent and unequivocal language the dignity and the worth of human personality.” When urging people to join the boycott of Montgomery’s segregated transportation system, he insisted, “We are not wrong,” because “If we are wrong, the Constitution is wrong.”

He drew on these documents to legitimize and motivate social activism. In his famous Mountaintop Speech, where he spoke about having “been to the mountain top” and “seen the promised land,” he recalled having been stabbed during a book signing. The knife’s blade reached the edge of his aorta, leading the New York Times to report that if he would’ve sneezed, he would’ve died. In a particularly moving passage of his speech, King reflected on surviving this brush with death:

I want to say that I am happy that I didn’t sneeze. Because if I had sneezed, I wouldn’t have been around here in 1960, when students all over the South started sitting-in at lunch counters. And I knew that as they were sitting in, they were really standing up for the best in the American dream. And taking the whole nation back to those great wells of democracy which were dug deep by the Founding Fathers in the Declaration of Independence and the Constitution.

Even when America “defaulted” on its promissory note, depriving Black Americans of equal rights and suppressing peaceful protests or free speech, King “refuse[d] to believe the bank of justice bankrupt.” Instead, he dreamt that the nation that would “rise up” and “live out the true meaning of its creed.”

For King, that rising up took the form of organizing, carrying out mass demonstrations, and engaging in peaceful protests. But he couldn’t avoid directly engaging with the law. In fact, the law often sought him out.

King was arrested several times on trumped up charges. He was arrested for “loitering,” (attempting to attend the arraignment of a man accused of assaulting his friend and mentor), “trespassing” (setting foot into an all-white restaurant), and “driving without a license,” (King did, in fact, have the proper license). He was the first person ever criminally charged in the state of Alabama with tax fraud, and it’s not hard to imagine why. Laws of all kinds are easily weaponized against political minorities, whether racial, religious, or ideological—or in King’s case, a combination of the three.

Even the issue of occupational licensure was intertwined with King’s activism. The New Orleans bus boycott, for example, was threatened by the fact that many of the city’s Black workers relied on buses for transportation to work. If civil rights leaders wanted to maintain the boycott, they needed to find another way of getting the boycotters to their jobs. But when these leaders asked volunteers to drive, they found that Baton Rouge required individuals to secure a taxicab license before getting paid, and getting a license required approval by a local commission—which was unlikely. Thus, the volunteer drivers could not afford to drive people for free, but they were barred, by law, from being compensated. Organizers were eventually able to work around this roadblock by collecting donations and distributing them to the drivers, “but the system was still economically weak. The boycott lasted ten days before the [protesters] w[ere] forced to agree to a compromise which maintained segregated seating on the buses.”

According to Timothy Sandefur, King ran into the same problem at the time of the Montgomery Bus Boycott. A year into the boycott, the city attacked it with “the legal weapon King’s lawyers had feared most,” an injunction demanding that the Montgomery Improvement Association (MIA) cease running a transportation network without a license. When the MIA went to get a license, it was denied. King was in the courthouse battling the legality of the carpools when a reporter told him the Supreme Court had declared segregation in public transportation unconstitutional, thereby ending the need for a boycott and vindicating equality before the law.

Even though King and other civil rights activists were the target of prosecution, their lawsuits often affirmatively shaped law for the better. This is perhaps no more apparent than with regard to the First Amendment. King was arrested multiple times for engaging in peaceful protests or staging sit ins, and he faced charges of disturbing the peace, marching without a permit, and even engaging in criminal libel. His cases and others were integral to Supreme Court precedent related to the vagueness doctrine, freedom of association, protections over donor anonymity, the right of non-profits to solicit contributions, and the right to engage in public interest litigation. The effect of the civil rights movement on the law, Randall Kennedy has written, was “not only a beneficial transformation in the substantive law of race relations, but also a blossoming of libertarian themes in First Amendment jurisprudence.”

It’s also true that King believed that there were limits to the legal system’s ability to effectuate meaningful change. On the one hand, judges could provide recourse after the democratic branches failed to protect the rights of Black Americans. But on the other, even after tremendous wins at the Supreme Court, including Brown v. Board of Education, states remained recalcitrant and only relented in the face of further organizing. King therefore believed that legal efforts must be combined with social action. Still, his experiences instilled in him an appreciation of constitutional law and legal representation. He wrote of the legal profession, “The road to freedom is now a highway because lawyers throughout the land, yesterday and today, have helped clear the obstructions, have helped eliminate roadblocks, by their selfless, courageous espousal of difficult and unpopular causes.”

King’s belief in our founding documents and the importance of constitutional law is often underappreciated. Happy Birthday, Martin Luther King, Jr., champion of freedom, equality, and our Constitution.