State legislators who shepherded the marijuana-legalization law are worried that local governments might inadvertently crimp sales by charging taxes that are too high.

A group of legislators put out a "local government toolkit" today in an effort to answer the myriad questions that were an inevitable part of the 610-page law passed just a few months ago.

Part of that toolkit warns local lawmakers to "proceed with extreme caution and avoid immediately taxing to the cap. We are already near the high-middle end of tax rates around the country, and it’s vital to allow the marketplace to mature before increasing tax rates."

“It is anticipated that it will take up to five years before the market is fully mature, so a taxation strategy should take this into account to avoid negatively impacting consumer movement into the legal marketplace and counterproductive taxation strategies," says the document put out by state Reps. Kelly Cassidy and Jehan Gordon-Booth, and state Sens. Heather Steans and Toi Hutchinson.

Buyers of marijuana already will face state tax rates between 20 percent and 34.75 percent, depending on the potency and type of product, whether it’s smokeable buds or gummy bears.

The state law also gives municipalities the right to charge their own taxes of up to 3 percent, as well as 3 percent in county taxes.

Legislators were hoping to keep the total tax rate below 30 percent.

"If you tax it too high, it makes it cheaper to buy on the illicit market," says Pam Althoff, a former state senator from McHenry County who is executive director of the Cannabis Business Association of Illinois, an industry group.

The state of Illinois hasn’t put out formal revenue forecasts, but a study by the Illinois Economic Policy Institute estimates annual sales of about $1.5 billion and tax revenue of $500 million for the state and $25 million for local governments once the industry hits full stride—based on a tax rate of about 27 percent.

“If you put the tax revenue first, you end up with less revenue,” Cassidy said.

If tax rates are too high, they’ll keep people from buying marijuana from dispensaries. “We’ve seen it play out in other states: The illicit market will underprice,” Cassidy said. “We know it takes time to get the market to full size and maturity.”

The Chicago City Council already has floated a proposal of taxing weed sales at 3 percent.

The Pew Charitable Trusts recently reported that the few states that have legalized recreational marijuana have a mixed record of accurately forecasting revenue. Given the fiscal constraints for the state and its towns and counties because of pension obligations, shortfalls could be particularly painful.

Pricing is just one potential problem ahead on the road to meeting the state’s ambitious timetable to begin selling recreational marijuana by Jan. 1.

One other provision of the law that’s proving to be a headache was giving municipalities the option to not allow retail sales of recreational marijuana in their communities.

Several suburbs, such as Naperville, are wrestling with whether to allow recreational dispensaries or not. The legislators are offering up draft legislation from cities such as San Francisco, Denver and Las Vegas to speed up the process, which can drag out because most municipal governments only meet monthly.

That’s critical because the state law relied on simply adding retail sales to the 55 existing medical dispensaries and allowing those license holders to each apply for an additional retail outlet. But that requires knowing which communities will allow such sales. In the meantime, the clock is ticking.

Adding to the problem is another bureaucratic headache: The state agency in charge of handing out retail licenses is taking a strict view of the language of the law, that medical dispensaries can only add retail sales at the exact locations that were operating July 1. But operators say they need bigger facilities for retail sales than some early medical dispensaries can accommodate.

One option is to clear up the language in a “trailer bill” expected this fall. “The concern there is timing,” Althoff said.