What has made America the most prosperous nation in history? Many other countries are as bountifully blessed with natural resources, so it's not just a matter of dumb luck. America's success springs mainly from two sources: our system of government and our human capital.

Historically, our government has promoted trade while keeping taxes and regulations relatively light. Moreover, it has preserved the rule of law: protecting private property, securing basic freedoms and upholding contracts.

Our people are critical as well. "American ingenuity" is a phrase recognized around the world. Ours is a nation of inventive minds, possessed of an innate can-do, entrepreneurial spirit. Immigrants are self-selected on the basis of courage, work ethic, ambition, drive and a yearning for freedom - economic, religious or political.

It is not too simplistic to say that the U.S. imports many of the best and the brightest minds and the hardest working people from the rest of the world. This is evidenced by the high percentage of the foreign born who start businesses (from Google to corner grocery stores), are valedictorians of their high school graduating class, win scientific awards, and own patents.

The combination of immigrant talent and home-grown ingenuity is a formula for economic growth and business creation. One must simply visit Silicon Valley or other high-tech corridors throughout the country to see this firsthand. The economic gains to the nation from legal immigrants with high levels of skills and unique talents are significant. Sadly our broken immigration debate is more about those who broke the law than about those playing by the rules and who are eager to contribute to our society.

A better legal immigration system is needed, along with a secure border and a willingness to enforce workplace laws. Admission policies must encourage economic growth and assimilation, not encourage people to cross our borders illegally.

It makes sense to have some limit on immigration, as all countries do. Here is why. Obviously, we cannot take in the whole world with any hope of successful assimilation. Therefore, "We the People" must decide who to put on the path to citizenship and who should be disqualified. Each year, we admit more immigrants on the track to permanent residency and citizenship than all other countries, only a few of which prioritize citizenship like we do.

Amnesty is not needed, however. We are a nation of laws, and those who enter the country illegally flout and degrade those laws. To allow illegal immigrants to jump ahead of those are playing by the rules undercuts the rule of law.

Another amnesty will almost certainly encourage more unlawful immigration. In 1986 Congress granted amnesty to 3 million illegal immigrants. Today we have 11 million.

Amnesty will also be costly, thanks to the welfare state. Compounding the problem, President Obama's administration actively recruits people to sign up for food stamps and other government benefits. Such practices make it all but impossible to maintain our tradition of opening our doors to the world's poorest, something that cannot work when the government itself is busily adding immigrant families to welfare. Means-tested welfare programs at the state and federal levels now cost nearly $1 trillion a year.

This is why we need a pro-growth immigration admission policy so those most prepared to contribute to the economy and lessen the tax burden can navigate the system. This could include foreign graduates in engineering and sciences, H1B immigrants with special skills needed by industry and investor immigrants.

At the same time, industries - such as agriculture - that traditionally depend on migrant workers should be able to bring in temporary guest workers with minimal government regulation and hassles, assuming taxpayers are protected. Innovative solutions like Helen Krieble's Red Card guest worker program provide a great start.

Even good ideas need to be pursued only at the right time, however. Now is not the right time. President Obama has shown he has little interest in enforcing existing laws, especially on immigration. Senate Democrats have already said they will take any immigration bills the House passes and add amnesty in conference. That means now is time for conservatives to develop an alternative vision, not legislation, on immigration that does not include amnesty.

Amnesty is a policy that proposes to fix a problem - illegal immigration - by rewarding those who created it. We favor a smart policy that preserves our immigrant heritage, stresses assimilation and strategically promotes the nation's economic interests.

 - Steve Moore is the chief economist and Derrick Morgan is the vice president of domestic and economic policy at the Heritage Foundation.