Lawmakers are taking another crack at a bill to prohibit employers from discriminating against workers who test positive for marijuana if they hold a prescription for cannabis.

Senate Bill 2543 would protect employees from termination or hiring discrimination when the workers test positive for pot if the workers have a state-issued card authorizing them to use medical marijuana.

However, the bill would allow employers to use a “fit for duty test” for medical cannabis users working in potentially dangerous occupations.

The Senate Commerce, Consumer Protection and Health Committee and the Senate Judiciary Committee approved the bill with some amendments Friday. Senators heard similar bills last year, but the attempts to move those measures forward failed.

Cannabis remains illegal under federal law, and the state Department of Public Safety opposed the measure. That department, which operates the state prison system, noted that the federal Bureau of Alcohol, Tobacco, Firearms and Explosives has declared that anyone who uses marijuana is prohibited from possessing firearms or ammunition.

Other employers such as the shipping company Matson are worried about liability if their employees use marijuana and work at “any potentially dangerous job.”

“Matson’s operations involve the use of heavy machinery, which if used incorrectly or under the influence of an intoxicant can cause death or serious bodily injury,” according to the testimony.

Matson said it maintains a strict zero-tolerance cannabis policy that applies to on- and off-duty use.

The Judiciary and Consumer Protection committees amended the bill Friday to exclude law enforcement officers and corrections officers; firefighters and water safety officers; and emergency medical workers, including any health care workers who might administer drugs to patients.

Also excluded from the bill under the amendments made Friday are employees who work with children, seniors or other “vulnerable” populations; civil defense emergency management staff; employees who operate heavy equipment, including many trucks; drivers who operate vehicles designed to transport 16 or more passengers; drivers for utility companies; and drivers who are subject to union contracts that include drug use prohibitions.

The Drug Policy Forum of Hawaii supports the bill, and said in written testimony that 16 other states prohibit employers from discriminating against workers based on their status as medical cannabis users.

“Medical cannabis patients face significant stigma due to longstanding misperceptions regarding cannabis and its uses, fueled by a long standing, costly ‘war on drugs’ that is disproportionately waged against those impacted by social detriments of health,” according to the Drug Policy Forum of Hawaii.

Cannabis use poses “substantially lower levels of preventable injury, preventable illness, and preventable death” than alcohol and tobacco, according to the Drug Policy Forum.