June 18 (Bloomberg) -- Welcome back, uncertainty. Readers with long memories may recall the era around 2010, when Republican leaders in Washington frequently railed against "uncertainty." In their telling, President Barack Obama's penchant for wrapping Washington in red tape and radicalism was the chief impediment to a sound economy. After all, how could businesses hire and invest amid uncertainty about future taxes and regulation?

The 2011 debt-ceiling fiasco, in which Republicans exacerbated uncertainty and heightened risk to reap political reward, cast their commitment to predictable governance in a somewhat suspicious light. Now the immigration debate reveals the party again locked in a bear hug around uncertainty.

The biggest obstacle so far to immigration reform has been an effort to tie citizenship for the estimated 11 million undocumented immigrants living in the U.S. to the achievement of security "triggers" along the southern U.S. border. Senator Marco Rubio of Florida has been uncomfortably straddling the issue for weeks.

An amendment from Texas Senator John Cornyn, which his fellow Republican John McCain of Arizona called "a poison pill," calls for "situational awareness" and "operational control" of the southern border for at least one year before the 11 million can apply for green cards. What does that mean? That the government is effectively monitoring ("situational control") the entire border and capturing at least 90 percent ("operational control") of illegal border crossers. Cornyn's amendment also mimics the existing Senate legislation -- which was negotiated by a bipartisan Gang of Eight and passed by the Judiciary Committee -- by requiring that the E-Verify System for tracking an employee's immigration status be fully in effect nationwide.

If you want to stop illegal immigration, the E-Verify component makes sense. But there are a few problems with tying the fate of 11 million people to border metrics. First, who gets to decide when 90 percent operational control is achieved? Cornyn would have the Department of Homeland Security and the Government Accountability Office jointly certify the trigger. But based on what factors? Illegal border crossers rarely wait around to be accurately tallied.

What if a future Congress cuts funding for border control and the 90 percent rate isn't achieved? On the other hand, what if the border becomes so impassable that illegal crossers switch to sea routes, arriving on the U.S. coastline by the boatload? Does that mean the border is secure?

Among those who, under the Senate legislation, would be granted Registered Provisional Immigrant status, enabling them to be in the U.S. legally without citizenship, the prospect of obtaining citizenship would likely unleash entrepreneurial energies. Immigrants are more than twice as likely to start a business as native-born Americans. From 1995 to 2005, one-fourth of technology and engineering companies started in the U.S. had at least one key founder who was foreign-born. Legal status would enable such immigrants to put down permanent roots and build lawful businesses without fear of immigration crackdowns or shifting political winds.

So far, so good. But what if your future citizenship is tied not only to your compliance in paying taxes and following laws, but to immigration and budget politics in Washington and events outside your control on a border that may be thousands of miles from your home? How does that influence your decision to build a business, buy a home, get married or invest in human capital such as a college education?

Wouldn't uncertainty -- the risk that citizenship might be long postponed or even denied -- be an important factor in decisions about how much you invest in your adopted country?

Right now, a near obsession with border security is damaging prospects for legislation that represents the best hope of immigration reform. Yet the border is a far different place than it was in 1986, the last time the U.S. granted a broad amnesty to undocumented immigrants. The U.S. Border Patrol, with more than 21,000 agents, has more than doubled in size since 2004. Electronic surveillance has proliferated. In 2012, border apprehensions were down 50 percent compared with four years earlier owing to the drastically reduced flow of illegal crossers. The bipartisan deal worked out by the Gang of Eight would add billions more to enforcement.

Immigration reform isn't an easy issue in conservative regions of the country. But leaving 11 million people at risk of permanent legal limbo solves nothing. Conservatives must decide whether they want immigration reform or whether they want to make a symbolic stand on the border. End the uncertainty.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)