Regardless of technicalities, income whatever its source, including income which is compensation for labor, has been unanimously been ruled as potentially taxable.
The 16th Amendment abolished the requirement for apportionment, which was its entire purpose.
The original reference cited (Tax protestor faq) is comprehensive in rebutting all sorts of such silly arguments.
Also, realize that a Federal agency operating under a law authorized by Congress may make regulations to properly enforce and put into action the law enacted by Congress. (Consider environmental & safety regulations, e.g. Does Congress have to approve or deny every drug with a new law? No, they tell the FDA to make the decision. Is that illegal? No.)
So there need not be a specific law in black letter which says that you must file a 1040 (surely the number of the tax forms are not generally specified by Congress), but the IRS’s power to compel information sufficient to carry out its operation as outlined by Congress is clear. The IRS has standing to obtain that information and impose penalties for failure to do so, and all courts have found this to be legal.
And case law is law that people must obey as well.
The law is not some inane computer program that James T Kirk can cleverly cause to self-destruct with some convoluted linguistic legalisms.
It is the intent of Congress that people pay taxes, and it is legal for Congress to have that power, and compel people to do so.
