(Photo: Ben Schumin / Flickr Now – not after the tar sands spigot is turned on – is the time to support the efforts of courageous Texas landowners who could stop Keystone XL’s administration-approved southern leg in its tracks.

Twenty-five environmental leaders recently signed on to an open letter to President Obama urging him to avoid any “deal-making” with the Canadian government and to reject a presidential permit for Keystone XL’s proposed northern leg. As the letter remarked: “Building Keystone XL will expand production in the tar sands, and that reality is not compatible with serious efforts to battle climate change.”

I share my colleagues’ objection to any deals between the United States and Canada over Keystone’s prospective northern leg, but what the open letter posted by 350.org ignored is the well-reported fact that the 485-mile southern leg of Keystone XL already is being built. Did the president engage in deal-making to facilitate this?

Regardless of what the president decides about the northern leg permit in 2014, Keystone XL’s southern leg – which is now 95 percent built – is ready to begin pumping more than half a million barrels of climate-destroying tar sands daily from landlocked Alberta to Gulf Coast port refineries by as early as the end of this year. This “reality is not compatible with serious efforts to battle climate change.”

Last spring, Obama made a special trip to Cushing, Oklahoma, to hold a press conference directing his administration to “cut through the red tape, break through the bureaucratic hurdles, and make this project a priority, to go ahead and get it done.” He said this about Keystone XL’s southern leg only months after announcing he was postponing, until after the election, a decision on Keystone XL’s northern leg.

This is classic bait-and-switch. By breaking Keystone XL into northern and southern legs, he was able to give his environmental base something it wanted (a “victory” to crow about), while giving TransCanada something it needed (access to port refineries).

When Obama released his climate action plan in June, he said, “The question now is whether we will have the courage to act before it’s too late. … I refuse to condemn your generation and future generations to a planet that’s beyond fixing.” He cannot now stand idly by while Keystone XL’s southern leg is completed and expect anyone to believe what he said. If the Obama administration could conjure up a way to fast-track construction of the Keystone pipeline, it should be able to conjure up a way to stop it.

The price the president would pay for such a courageous act likely would be high, but it would help ensure his legacy as a president, and as a father, who saw the dangers of the gathering storm and chose to do something before it was too late. Of course, the odds of him making such a bold move are slim to none, absent massive public pressure, which will not be forthcoming as long as his friends in the environmental movement continue coddling him, instead of calling him out.

Now – not after the tar sands spigot is turned on – is the time for movement leaders to support the efforts of courageous Texas landowners like Michael Bishop, who has singlehandedly filed a series of lawsuits that could stop Keystone’s southern leg in its tracks. And let’s not forget about the fraud case Texas landowner David Daniel painstakingly developed against TransCanada that three attorneys told him stood “a good chance” of winning. David, like Michael, got no help, despite sharing his case with every environmental group and attorney he could think of. It now sits on a shelf collecting dust.

There are many possible roads to victory, but the surest path to defeat is to not even try.