Constitutional limitations on the taxing power

[A18]

Which of the following are constitutional?

Tax hikes as they apply to the salaries of federal judges.
Federal taxes on the salaries of state officers.
Levying tariffs for protectionism, and not solely for revenue.
Federal taxes designed to have a regulatory effect.
Federal deductions for state and local taxes, though these taxes vary from state to state, locality to locality.
Federal taxation of state activity.
Federal income taxes of 100% or more.

[Emsworth]

Tax hikes as they apply to the salaries of federal judges: Constitutional (as long as the hike is general, rather than a specific hike on judicial salaries)

Federal taxes on the salaries of state officers: Constitutional (as long as the tax is general, rather than specific to state officers' salaries)

Levying tariffs for protectionism, and not solely for revenue: Constitutional. Congress has the power to regulate foreign commerce.

Federal taxes designed to have a regulatory effect: If the regulation pertains to interstate, international, or Indian commerce, then it is constitutional. Otherwise, the tax is unconstitutional.

Federal deductions for state and local taxes, though these taxes vary from state to state, locality to locality: Constitutional. Although the values of the deductions are nonuniform, the rule under which the deductions apply are. It is no different from any other kind of deduction.

Federal taxation of state activity: Unconstitutional.

Federal income taxes of 100% or more: Unconstitutional.
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