There is a familiar truism about what the President of the United States can do with the limited powers he or she is given by Constitution and Congress. One of those powers is the use of directives and executive orders to organize the federal government.

The truism is “What can be done with the stroke of a pen can be undone with the stroke of a pen.” In other words, subsequent presidents can rescind executive orders because they are not permanent. Donald Trump has promised to fire up his shredder to get rid of all of the orders issued by President Obama.

There are a few fine points to understand here. First, executive orders are not the same as federal regulations. It takes a long time and lots of public input to finalize regulations, and it takes nearly as much work to repeal them. Some of what Trump wants to undo falls in the regulation category.

Second, most executive orders (as well as presidential directives, proclamations, and memoranda) are trivial. Others are important. They are all easy to rescind, but that does not mean a new president should.

Here, for example, is a small sample of the presidential orders that Trump, if he were to win the election, should think about twice before consigning them to the shredder. Obama has directed federal agencies to:

• Save taxpayers as much as $18 billion by requiring federal agencies to conserve energy.

• Make clear in America’s dealings with other nations that the United States considers violence against women and girls anywhere in the world to be a human rights violation.

• Use their purchasing power to support healthy market competition between businesses.

• Improve access to mental health and suicide-prevention services for war veterans and their families.

• Take steps at the Pentagon to prevent civilian casualties during war operations and to publicly report civilian casualties when they occur.

• Deny safe haven in the United States for perpetrators of mass atrocities.

• Block North Korea’s access to any property and interests in the United States and deny entry to any immigrants from North Korea.

• Protect the American people from public disclosure of their personal information.

• Make recommendations on how to build partnerships and trust between police and local communities.

• Improve the government’s capabilities to free Americans citizens taken hostage abroad.

• Prevent wasteful spending on travel, use of federal vehicles, printing and other functions.

When it comes to the health and safety of the American people and to national security, the biggest threat is Trump’s promise to pull the United States out of the historic international climate agreement reached last December in Paris. The agreement is the result of more than 20 years of negotiations. Two-thirds of the nation’s registered voters supported it. The withdrawal of the United States – the world’s second largest source of greenhouse gas emissions – would very likely cause the agreement to collapse.

Trump’s threat to rescind everything Obama has done makes a good applause line at his rallies, but it’s one of several indications that the businessman knows too little about the government he wants to lead.