Following dozens of arrests and citations at a recent concert, police hope to encourage concertgoers of all ages to leave the pakalolo at home and not to drink alcohol at public venues such as the Waikiki Shell if they are under 21.

A police advisory was issued just days before today's scheduled Ziggy Marley performance at the Waikiki Shell at 5 p.m. Marley is the son of legendary reggae rocker Bob Marley, and like his father, is an advocate of legalizing marijuana.

The Honolulu Police Department on Wednesday issued a news release urging those planning to attend concerts not to party hearty with weed or otherwise while enjoying the music.

Police spokeswoman Michelle Yu said the admonition is not aimed specifically at Marley fans. It was meant to be a general public heads up, along the lines of warnings about police roadblocks during the high school graduation period or reminders about the proper use of fireworks on New Year's Eve.

HPD officers working with Honolulu Liquor Commission investigators arrested 30 people at a Honolulu radio station's "birthday bash" concert July 24-25 at the Waikiki Shell. The arrests were primarily for marijuana use, police said.

At the same concert, police and liquor investigators handed out 21 citations, all but one of them for underage drinking.

"It's unfortunate that a few people still don't get it," said Maj. Gregory Lefcourt, whose police district includes the Waikiki Shell. "Although the situation has improved, we're still seeing illegal activity at concerts."

Lefcourt said those under the age of 21 who go to concerts at the Shell or elsewhere should be aware of Hawai'i's "use and lose" law that took effect two years ago.

People under 21 can have their driver's license suspended for 180 days or longer if they are caught illegally purchasing, possessing or consuming alcohol, Lefcourt said.

In the case of minors who don't yet have a license, a judge may postpone their ability to get a license for 180 days or until they turn 17.

"I was young once, and I remember how important it was to have a driver's license," Lefcourt said. "We're asking teens to be responsible and think about the consequences of their actions."