Marshall says a gas tax should not be considered a user fee because unlike a tax, a user fee gives the consumer a choice to either pay, or not to pay. He sites the fee to enter and park at a national park, as well as the use of toll roads as examples that incur user fees. People have the choice to pay to park, or to use the less traveled tollway.
"To qualify as a user fee, you must have a choice as to whether or not you pay it. It also must relate directly to a particular service that you can accept or reject, and to the number of times you use that service."
"Why do all these labels matter? Aren't they just semantics? No, because labels influence policies."