CHICAGO (AP) — Illinois’ concealed carry law doesn’t allow patrons to bring firearms into a bar or restaurant that predominantly sells alcohol, but those restrictions don’t apply on a party bus, where passengers provide their own booze.

A Chicago ordinance approved in September requires party bus drivers to call police if patrons throw a beer bottle out the window or smoke marijuana. But a string of six shootings with injuries in 14 months involving party buses pointed to a gray area in the rules, the Chicago Tribune reported.

The ordinance doesn’t mention whether passengers can bring a gun on board because policies dictating where someone can legally carry a loaded gun must be decided at the state level. The ordinance does say the driver must call authorities if a weapon is discharged.

“We’re not doing anything to limit one’s Second Amendment rights because that is covered by state law,” said Alderman Brendan Reilly, who proposed the September ordinance. “My personal preference would be that guns are not allowed in party buses.”

While some buses have a no-weapon policy specific to their company, staff members have said it can be difficult to enforce such a rule.

“Do we check every customer? No. It would be hard to be out there frisking everyone,” ChiTown Party Bus owner Chris Vecchio said. He added that his contracts note that his staff has the right to search anyone or any item brought on the party buses.

Illinois Council Against Handgun Violence executive director Colleen Daley said her organization is continuing to fight for banning guns in any establishment where people consume alcohol, including party buses.