Ask your Congressman and other authorities
Beware of the "answer" you may get. The non-answer (like this one) may say that Congress during the Civil War authorized the Commissioner to do all that the IRS now does (unstated: This was during martial law and the only wages taxed were government employees). This non-answer is easily rebutted, and even the IRS no longer publishes the 1862 Commissioner story. And it doesn't even answer the question of what authorizes them to use the name. (hint: because they are a foreign bankruptcy receivership that took over when the U.S. went bankrupt in 1933 and our gold was seized and ALL assets of the United States were seized).
W-4 Withholding is only for Gift and Estate Tax (IRS tax class 5), not for Income Tax (IRS tax class 2). There is no withholding authorized under the Income Tax Code (which is subsection A of the Internal Revenue Code). I have never been able to get an answer. Is it because Social Security FICA is for your future estate? Or is the gift and estate tax for your gift to the government's estate because you are government property and all your labor belongs to them? Or is income tax a Gift to the government? Or is your take home pay the government's Gift to you of a slave's living allowance?
Form I-9 is authorized by the Migrant and Seasonal Agricultural Workers Protection Act. Is it the intent of this act to force employers to pay minimum wage to newly naturalized migrants (replacing this prior regulation.)
As you advance in your path to freedom you will get comfortable asking politically uncomfortable questions. You will eventually stop when you realize official answers are inane. By then you will have enough non-answer darkness to guide you into to the light.
Later on, you will write letters to the IRS to get your Individual Master File and your AMDISA file. You may be surprised that you owe tax for operating a business that you had no knowledge of. I found out that I owe income tax for operating an underground coal mine in the Virgin Islands. The depleting of mineral resources of the United States is, of course, a taxable government granted privilege. A "revenue taxable activity".