MINNEAPOLIS — A Hennepin County judge won’t stop the state’s new ban on synthetic drugs from taking effect today.

So as of midnight, it will be illegal to have or sell synthetic drugs, including fake marijuana, bath salts and other chemicals, like the one blamed in a mass overdose that killed a 19-year-old last spring.

Hennepin County District Court Judge William Howard said it’s too soon to decide whether the new law is too vague, because no one has faced criminal charges under it.

Several retailers want to stop the ban, including Down in the Valley, Last Place on Earth and Disc and Tape.

The ban outlaws substances “substantially similar” in structure to illegal drugs. The retailers say customers and stores won’t know if they are breaking the law.