It’s not difficult to understand why a visitor impact fee has such broad support. As an idea, it’s appealing. Make tourists pay to offset their impact on our state? Not only does that have an innate sense of justice to it — like someone washing their own dishes — it also has the appeal of doing something useful with someone else’s money.

However, there can be a world of difference between an appealing idea and something that is practical and workable in real life. That’s where the visitor impact fee falls short.

For starters, there’s the challenge of defining a “visitor.” Senate Bill 304, the version of the fee that is still alive at the state Legislature, says a resident is anyone who has paid Hawaii income taxes in the past year, has a Hawaii ID or who can produce some kind of residency documentation, such as a utility bill or a letter from a state agency.

In fairness, this is a logical way to separate residents from nonresidents for statutory purposes. But it can lead to strange results.

Under this definition, American talk show host and film star Oprah Winfrey is a resident because she can produce a utility bill for her Maui home. But Iam Tongi, the “American Idol” contestant whose family was “priced out of paradise” and now lives in Seattle, is a “visitor.”

Facebook founder Mark Zuckerberg, who lives part time on Kauai, is also a Hawaii resident for the purposes of this fee, but your cousin who had to move his family from Kauai to Nevada two years ago is a “visitor.”

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SB 304 also proposed that these “visitors” would have to pay a $50 license fee in order to visit any park, beach, forest, hiking trail or other natural area owned by the state. Not only would this incentivize tourists to plan trips that involve only beaches and parks that aren’t owned by the state — it means that mainland relatives invited to grandma’s birthday party at Malaekahana State Recreation Area would have to pay to attend.

And where would that money go? It wouldn’t go to fix roads, renovate airports, improve schools or clean up beaches. Instead, it would go into a special fund that would be distributed to agencies and environmental groups for vaguely defined conservation and environmental purposes.

In other words, a visitor impact fee is unlikely to have much of an impact on our daily lives. It would be more useful to think of it as a direct funding source for environmental causes.

The bill includes penalties for those who don’t comply, raising the issue of how it will be enforced. Would police have to patrol state beaches, asking for proof that everyone is a resident? It’s a civil rights nightmare in the making.

Of course, that’s assuming the bill is enacted. Given that the U.S. Supreme Court frowns upon laws that inhibit travel between states and dislikes measures that tax nonresidents and residents differently without a rational basis for doing so, a visitor impact fee would be subject to an immediate constitutional challenge.

This is not to suggest that we can’t use visitor dollars to address the impact of tourism on our natural resources. But let’s do it transparently, through the general fund, and without risking legal challenges over arbitrary distinctions as to who is or is not a true Hawaii resident.

Malia Hill is policy director for the Grassroot Institute of Hawaii.