When does free expression become tougher to defend as a constitutional right? When it's neither free nor particularly expressive. Some of the activity conducted along Waikiki's "street performance" segment of Kalakaua Avenue comes closer to commerce than an exercise of pure freedom.

Knowing where to draw the line is a challenge for Honolulu's law enforcement authorities — even more so now with a key federal ruling from the judicial circuit that includes Hawai'i.

That 9th Circuit Court of Appeals ruling struck down Seattle's permitting system as an unconstitutional restraint on speech.

So elected leaders here don't want to impose new regulations for Honolulu and, given the court ruling, they shouldn't.

But some street "artists" on Waikiki's signature thoroughfare still seem to be running purely commercial enterprises, and that must be reined in.

Honolulu police and prosecutors should rely on laws already on its books to curb the growth of Waikiki street activities, enlisting the help of the community to keep them within legal bounds.

Some of the "artists" seem to be testing those boundaries; they hardly seem to qualify as protected expression.

It's hard to see, for example, how individuals offering services such as full-body or foot massages and hair-braiding are practicing free speech.

But until the definition is more fully defined in court, police can't be expected to exclude select activities.

Instead, the key is enforcement of the rules against peddling in Waikiki, which allows donations to be solicited, but not demanded as a fee.

The burden can't fall exclusively on tourists, who may be happy to pay, however they're asked. Or, they may be unwilling to break from their vacation to lodge a complaint.

So residents and the business community should step up: Those who see the activity as intrusive or unfair to paying tenants should monitor the situation and offer more help with prosecution when "artists" push the limits of the law.

Neighbors and merchants are in a good position to serve as witnesses if activity strays too far from artistic expression and too close to commerce.

Many people do enjoy a bit of the carnival atmosphere on the street, and it seems a small matter compared with the more pressing duties of keeping Waikiki safe and pleasant.

But it remains the duty of police and the Waikiki community to keep this small carnival from becoming a circus, one that annoys rather than entertains.