On Friday, the Obama Administration’s Department of Homeland Security issued a memorandum telling U.S. immigration officials how they should “enforce the Nation’s immigration laws against certain young people who were brought to this country as children and know only this country as home.”

The Administration’s move is an attempt to implement major elements of the DREAM Act, a controversial bill that’s been introduced in both Democratic- and Republican-controlled Congresses but has always lacked the votes to be passed into law.

Having failed in the legislative branch, how can the executive do this?

The Administration insists it has wide “prosecutorial discretion” when it comes to enforcing immigration law. No one doubts that judges, prosecutors and law enforcement officers should have discretion about what charges to bring and how to handle particular cases. There are always exceptions to the rule. But Friday’s order, which uses the term discretion some 10 times, seems to go beyond discretion to the point of creating a policy scheme contrary to existing law. The exception has become the new rule.

Imagine a police chief instructing everyone on the police force to issue no speeding tickets to anyone under age 26, regardless of how fast the driver was going. That’s not discretion; it’s a policy instruction that changes the meaning of the law. Former Bush Administration lawyer John Yoo goes further:

Imagine the precedent this claim would create. President Romney could lower tax rates simply by saying he will not use enforcement resources to prosecute anyone who refuses to pay capital-gains tax. He could repeal Obamacare simply by refusing to fine or prosecute anyone who violates it.

As a policy matter, there are legislative solutions to the problem posed by the situation that some children at a very young age were brought by their parents to the United States illegally. A proper solution  would uphold the principles of immigration reform and not open the door to a blanket amnesty. Finding an actual solution through the legislative process would give the law legitimacy and more permanency, and it might even result in a bipartisan agreement. It would be part of a larger effort to find effective, reasonable and pro-immigration solutions to safeguard the nation’s borders, promote the rule of law, and administer a fair and positive immigration and naturalization system.

The fundamental problem is that the Administration is trying to implement laws that Congress hasn’t passed. The President himself has admitted that he doesn’t have the constitutional authority to implement the DREAM Act: “The idea of doing things on my own is very tempting, I promise you, not just on immigration reform. But that’s not how our system works. That’s not how our democracy functions,” he told Hispanic activists last year.

Indeed, the order seems to recognize its constitutional shortcomings: “This memorandum confers no substantive right, immigration status or pathway to citizenship,” it admits. “Only the Congress, acting through its legislative authority, can confer these rights.” Yet what the Administration can’t achieve as a matter of law it seems to be focused on accomplishing as a matter of fact.

The Administration is making a habit of overstepping its bounds. Last fall it issued sweeping waivers of the No Child Left Behind Act if states would implement national education standards not authorized by Congress. “Congress hasn’t been able to do it, so I will,” Obama announced then. Then there are the President’s recess appointments when the Senate isn’t in recess. The list goes on.

In our system of government, Congress is the legislative branch and is responsible for making the laws. Presidents are supposed to “faithfully execute” the laws to the best of their ability, not reshape them to suit their own policy goals.