Let's try Title 26, Subtitle A, Chapter 1, Subchapter A, Part I, Section 1.
That imposes a tax based on the income of any US citizen or resident alien from whatever source derived.
Let's try Title 26, Subtitle A, Chapter 1, Subchapter N, Part II, Section 871:
Except as provided in subsection (h), there is hereby imposed for each taxable year a tax of 30 percent of the amount received from sources within the United States by a nonresident alien individual... (followed by a description of what gets taxed, which refers extensively to Part I, Section 861).
Subchapter N, Part I, Section 861 only gives you the rules for determining what is and isn't taxable income if you fall under Subchapter N, Part II, Section 871--i.e., if you are a nonresident alien.
If you're not a nonresident alien, you compute your taxable income using Chapter 1, Subchapter B.
Yes, the rules ARE different if you're a US resident as opposed to a nonresident alien.
That imposes a tax based on the income of any US citizen or resident alien from whatever source derived.
Actually, it imposes a tax based on the taxable income, and the income must be derived from a source. And if the law defines a given term, it doesn't matter how many expansive modifiers are used in connection with it, it still means what the law says it means.
26 USC § 5841 states that "[t]he Secretary [of the Treasury] shall maintain a central registry of all firearms in the United States which are not in the possession or under the control of the United States. But this law has a far more limited application than this section by itself would seem to imply. In 26 USC § 5845(a) it is made clear that the term "firearm" in these sections does not include the majority of rifles and handguns (while the term "firearm" in basic English obviously would), but does include poison gas, silencers and land mines.
Just as "all" doesn't change the statutory definition of the term "firearm," the term "whatever" doesn't alter the broadness of the term "source" in the statutes.
In order to determine the taxable income of a taxpayer, the regulations state:
The rules contained in this section apply in determining taxable income of the taxpayer from specific sources and activities under other sections of the Code, referred to in this section as operative sections. See paragraph (f)(1) of this section for a list and description of operative sections. [26 CFR § 1.861-8(a)(1)]
To break down this terminology, the "other sections of the code," known as "operative sections," are those pertaining to "determining the taxable income of the taxpayer from specific sources and activities."
The list of "operative sections which require the determination of taxable income" as set forth in (f)(1), does not apply to most US citizens.
And an ancient canon of statutory construction states, "expressio unius est exclusio alterius" - expression of one thing is the exclusion of another.
Stating in law that "for the purposes of this code, the term 'holiday' includes New Year's Day, Labor Day, Thanksgiving, and Christmas" does not mean that the term "holiday" might also possibly include Veteran's Day.
The operative sections which require the determination of taxable income are listed in (f)(1), and under "expressio unius est exclusio alterius," these are the only operative sections which require the determination of taxable income.