here is a reason our government has been a great democracy for more than 200 years, and it's one we don't often reflect on.

The patriots who created our government divided it into three parts that have held together like a delicately balanced watch: a president to defend us, a Congress to represent us, and a court system to ensure justice and interpret the law.

But the greatest function of these three branches is to hold one another in check, to make sure no one branch, and no man, is above the laws of the land.

In our nation's capital, that balance, which has protected our liberties, is in growing jeopardy. In recent years, the executive branch, led by the president, has repeatedly decided that it can ignore the other two branches.

Last week, more than 5,000 of my fellow lawyers have come to Honolulu for the 129th annual meeting of the American Bar Association. While we have many goals and programs, our most urgent task is defending the system of checks and balances that protects our democracy and our liberties.

On July 24, a blue-ribbon bipartisan task force I appointed reported unanimously that President Bush and other recent presidents have engaged in a practice that violates the U.S. Constitution. They have issued written documents, known as presidential signing statements, that claim the power to ignore newly signed acts of Congress.

In effect, presidents have told Congress, "I will not enforce a law with which I disagree."

In February, another ABA task force concluded that the administration's unilateral decision to eavesdrop on Americans — without consulting Congress and the courts — violated a national security law that has been honored by Democratic and Republican presidents since 1978.

The issue was the same. Presidents can authorize eavesdropping to protect our national security. But this awesome power, to invade the most private communications of Americans, is too great to be held by just one branch of government. There must be checks and balances from the other two branches.

I want to stress that our concerns are not directed at the current president. Presidents have repeatedly misused signing statements to bypass Congress since the Reagan administration. The practice is wrong, and dangerous, no matter which president or which party employs it.

Why is this notion of separation of powers — the idea that the courts, Congress and the president each have distinct duties and limited powers — so critical?

The short answer is that it's the law. It was the brilliant solution of our nation's founders to a problem rooted in simple human nature.

Great men such as James Madison and Thomas Jefferson knew our leaders would be human, not angels. They would be tempted to expand their power, and ultimately abuse it. The U.S. Constitution, as these great men crafted it, was designed to check this impulse.

That is why, in the case of surveillance, police officers need court approval to search homes, to make sure they have adequate cause. Likewise, when it comes to enacting and enforcing new laws, the Constitution is especially clear.

Congress, as elected representatives of the people, passes legislation. The president must sign a bill and execute it or veto it. The courts apply the law in specific cases and decide disputes over whether a law is unconstitutional.

As president of the ABA, I became deeply concerned in April, when I learned that presidential signing statements were being used to bypass this system of checks and balances.

As Boston Globe reporter Charlie Savage documented, Bush had issued written statements proclaiming his right to ignore 750 legislative provisions, on the grounds that they infringed on his power or otherwise violated the Constitution.

The number has since passed 800 — more than that of all previous U.S. presidents combined. In one extraordinary example, the president signed the "McCain Amendment," a law banning torture of prisoners by U.S. personnel — only to issue a statement saying he reserved the right not to enforce it.

Officials under the first Bush and President Clinton, who also issued similar signing statements in more limited numbers, have tried to defend the practice, saying that presidents cannot be expected to enforce unconstitutional laws.

But they have not clearly explained why the president should sign flawed laws in the first place. As the ABA Task Force on Presidential Signing Statements and the Separation of Powers Doctrine made clear, the president can — and should — veto any law he finds objectionable.

What a president cannot do is sign a law and then ignore it.

Whereas Congress can override a veto with a two-thirds vote, it cannot override a signing statement. And it is the courts' job, not the president's, to decide whether a law is constitutional.

I am extraordinarily proud of the work of this distinguished task force, which includes conservatives and liberals, and Republicans as well as Democrats.

Some have suggested that these checks and balances are ill-advised in a time of conflict and therefore need to be set aside. In fact, that suggestion is itself ill-advised. Setting aside checks and balances would destroy the essence of our constitutional government.

President Franklin D. Roosevelt used the veto 635 times, and we survived the Great Depression and World War II. In this age of electronic documents, vetoed bills can be revised and voted on within hours — barely a hiccup, let alone an issue that justifies an enormous expansion of executive power.

Where Congress and the president simply can't agree, the ABA task force recommends a process by which either party can submit disputed legislation to the federal courts, whose job it is to interpret and apply the law.

How does this affect you? Our government honors your personal rights because each branch has legal limits. Once any branch breaks free of those limits — if, in this case, the legislatures and courts are shoved to the margins — the rights that we take for granted can become easy targets.

There are signs that Congress and the courts are beginning to stand up to excessive claims of presidential power. But these branches can only do their jobs if you do yours.

Unchecked power was one of our founders' greatest fear. When leaders overstepped their bounds, they counted on an informed public to understand the dangers and demand that those leaders back down.

Make no mistake. They were counting on you.

Michael S. Greco is president of the American Bar Association. He is a Boston trial lawyer with the firm Kirkpatrick & Lockhart Nicholson Graham. He wrote this article for The Advertiser.