President Barack Obama is reportedly considering using prosecutorial discretion to effectively legalize millions of illegal immigrants.

He shouldn’t, for four reasons:

1. It would be an abuse of executive power for Obama to grant millions of illegal immigrants amnesty. The level of immigration should be determined democratically through our elected representatives, particularly Congress, which has authority to “establish an uniform Rule of Naturalization.” Obama disregarded the separation of powers in the Department of Homeland Security’s inappropriate Deferred Action for Childhood Arrivals memorandum, which essentially protected young adults brought to this country illegally as children from deportation. Any further legalization would raise even more serious concerns.

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It is unjust for the president to override the people’s determination (expressed through Congress) of how many people are welcome as residents of the United States. Prosecutorial discretion does not give the president a general license to ignore congressional statutes

2. It’s not fair to prospective immigrants, legal residents, and American citizens. Such presidential nullification of established immigration law is unjust to those who decided not to come to the United States because they would be doing so without authorization. It is also unjust to the millions of Americans and resident legal immigrants who followed the rules.

Moreover, it is more difficult to apprehend dangerous criminals at the border if the Border Patrol has to deal with an increasing number of illegal immigrants crossing the border. That will increase the cost and/or decrease the effectiveness of protecting the American people—an unjust result.

Refusing to uphold the law equally by making special exceptions for favored groups fits the pattern of unfairness emanating from Washington.

3. Amnesty would be extremely expensive. Given the government’s past difficulties with immigration enrollment programs and an existing backlog of at least 4.3 million people waiting for green cards, an administrative amnesty of up to 5 million individuals would have significant costs and cause major difficulties.

An amnesty-today policy would encourage more illegal immigrants to come in hopes of a future amnesty. The cost of the policy is therefore larger than just the administrative cost. Illegal immigrants who reside in the United States pay some taxes but consume more in government benefits, such as education.

4. Amnesty doesn’t work. If Obama pursues an administrative amnesty of millions of people, potential future illegal immigrants might think (wrongly) that they could qualify under this grant of amnesty or (rightly) that another amnesty is likely in the future if they can avoid deportation in the meantime. The end result will be more illegal immigrants crossing our borders.

This piece is adapted from the “Administrative Amnesty: Unjust, Costly, and an Incentive for More Illegal Immigration” backgrounder.