I have previously described in detail the reforms that America’s immigration system needs. In this post, I want to highlight what I think the general principles behind those reforms should be. Three basic principles should guide immigration reform: openness, equal treatment, and flexibility. Reform should make America more open to immigrants, should treat all immigrants equally as individuals, and should be flexible enough to respond automatically to changes in the economy or society.

1) Openness to new immigrants. Reform should make it easier to immigrate legally, not more difficult. This pillar protects the rights of Americans to associate, contract, and trade with people born in other countries. These people might be their family members, friends, employees, or employers, but ultimately, restrictions on immigration are restriction on the liberty of Americans. Reform should recognize the presumptive right—overcome only for very good reasons—of Americans to freely interact with foreigners on U.S. soil.

Of course, the freedom to associate across borders also benefits Americans—even those who don’t participate directly with the immigration system—by expanding the pool of employees, consumers, investors, and entrepreneurs who produce goods and provide services that improve the quality of life of all Americans. The social capital that immigrants bring with them makes America a stronger, safer country. Immigrants marry, have children, and participate in religious groups at higher rates than the U.S.-born population, and it is precisely for these reasons that they have much lower rates of criminality.

As a practical matter, there are many ways to move toward a more open immigration system. My list of reforms gives specific examples. But here is a general blueprint: grant indefinite work visas to anyone with a job in the United States, confer legal permanent residency on anyone who works for 5 years, and remove the quotas on green cards for immediate family members—adult children and siblings of U.S. citizens as well as spouses and minor children of legal permanent residents.

2) Equal treatment for new immigrants. America has a long legacy of discriminating against certain types of immigrants, from the Chinese Exclusion Act to the Asiatic Bar Zone to the National Origins Quota System. Unfortunately, this legacy is not entirely purged from the statute books. Today, the government still attempts to micromanage the ethnic makeup of legal immigrants by limiting nationals of any particular country to no more than 7 percent of the total green cards. These “per-country caps” discriminate against immigrants from high-demand countries like India, China, and Mexico, while discriminating in favor of those from less populous countries like those in Europe. The caps are not only an affront to the fundamental principles of fairness but they are economically harmful, forcing immigrants with more experience and higher wage offers to wait longer than others.

Last year, President Trump introduced more discrimination into the system by banning all entries from six countries. This effectively imposes a country quota of zero for Iran, Libya, Syria, Somalia, and Yemen. This means that even if an Iranian or Syrian is eligible for a green card under the normal channels, they would still be barred from immigrating. The president previously labeled this an extension of his “Muslim ban” concept. In order to end this discrimination, and prevent it from returning, Congress needs to repeal the per-country limits and bar the president from reimposing similar limitations without explicit authority from Congress.

3) Flexibility to changes in the economy and society. Congress has not updated America’s immigration system in 28 years. During that time, America’s population has grown by a third, and its economy has doubled. Yet the immigration quotas and categories have not changed at all. In order to prevent the immigration system from becoming antiquated, it’s not enough for Congress to merely update it based on what would be best for today—it needs to build a system that is flexible enough to adapt to changes that will happen in the future. Otherwise, the new system will become outdated soon after it is implemented.

Ideally, Congress would end arbitrary quotas on immigration. The government should impose qualitative, not quantitative limits, on immigration. Hard numerical limits are the most rigidity-inducing aspect of the legal immigration system and cause the most harm, but if Congress does maintain quotas, it should go beyond merely updating them. It should link family-based quotas to population growth (or the number of families in the United States) and link employment-based quotas to economic growth, growing as the economy grows.

This would prevent the numbers of immigrants from becoming outdated, but the categories and regulations under which those immigrants enter also fall out of line with the needs of the economy. Consider the fact that there are no programs for lesser-skilled temporary workers who want to work in year-round jobs because Congress in 1990 believed that employers only needed seasonal workers. While Congress can plug the holes as best it can, it should also grant the ability to states to sponsor immigrants based on whatever criteria that the state wants. Canada already has this type of immigration program for its provinces. This would allow states to essentially invent new green card categories, even while the numbers remain largely the same.

With these principles in mind, Congress can construct an immigration system that will provide for America’s economy and society long into the 21^st century.