Julius Caesar is reputed to have said, "The die is cast" as he crossed the Rubicon and headed south with his army to administer the coup de grace to what little was left of individual liberty under the old Roman Republic.

President Obama has been doing some casting of his own of late, as evidenced during the State of the Union address in his threat to Congress regarding global warming. First came the warning: Congress must pass a cap-and-trade bill to combat global warming because, Obama said, "the 12 hottest years on record have all come in the last 15. Heat waves, droughts, wildfires, floods, all are now more frequent and more intense." (Set aside that, as the Climate Depot's Marc Morano documents, the facts make it abundantly clear that the president is quite wrong on each point in that sentence.)

Then came the threat: "And if Congress won't act soon to protect future generations, I will. I will direct my Cabinet to come up with executive actions we can take."

It's not a new threat. In fact, Obama made this same threat in 2010 toward the 111th Congress -- which had Democratic Senate and House majorities -- when it considered multiple cap-and-trade proposals, including the president's.

The Democratic House approved a cap-and-trade bill, but it died in the Senate, because enough senators knew utility rates would "skyrocket," just as Obama promised in 2008.

But things are different now that Obama no longer faces re-election. There is little to restrain him from making good on his threat. And there's the rub: The Constitution says Congress makes the law, the president enforces it. He can veto laws he dislikes, but he can't make his own laws and exclude Congress.

By renewing his threat, Obama has marshaled his troops on the north shore of his Rubicon, needing only to give the command to cross over. The stark reality is that, unless the legislative branch is willing to block him in the strongest possible way, it won't much matter what Congress does.

Here's why: If Congress doesn't pass a cap-and-trade bill as Obama directed, a blizzard of executive orders will issue from the White House, along with a flood of companion regulations from the Environmental Protection Agency.

Or Congress can do as Obama demands and approve a cap-and-trade bill. Either way, cap-and-trade becomes a reality, and Congress is exposed for the hollow shell of its former self that it so often seems these days. But if the law is whatever the chief executive decrees, not what the people's representatives approve in Congress assembled, then America is no longer governed by the rule of law.

There is only one way to keep Obama in check: Congress must tell Obama there will be no cap-and-trade program, then defund his subsequent executive orders and regulations to the contrary.

But wait, Harry Reid and the Democrats control the Senate, and they will back Obama, right? They do and they may, though they didn't the last time cap-and-trade was before the Senate.

Even so, the House Republican majority can make sure the program receives no funding if they have the guts to stand firm against the Obama threat. They can simply refuse to approve one dime for it, exactly as the Constitution provides -- no matter what the New York Times editorial page calls them, and even if Obama shuts down the government to force the issue, as he might choose to.

My guess is it won't come to that, and that in the end, House Republicans will strut and shout for show, even as Senate Democrats ferry Obama across his Rubicon.

Mark Tapscott is executive editor of The Washington Examiner.