With marijuana legalization spreading, employers have begun to reconsider their substance abuse policies. They are in fact making them tougher.

As a first, the Society of Human Resource Management asked 623 HR managers in states where marijuana is legal about their drug policies.

Unsurprisingly, getting high while on the job is largely frowned upon, SHRM found, regardless of legality. It turns out that a large number of workplaces also won’t hire employees who smoke on their own time.

Marijuana is legal for recreational use in the nation’s capital and four states, including Colorado. In almost 20 others, it’s allowed for medicinal purposes.

More than 50% of the HR managers surveyed said they have policies, or plan to implement them, restricting the employment of marijuana users.About 38% said they will flat-out reject users even if they claim it is for medical reasons. 6% said their policy will exclude only those who partake for fun.

“There is what I consider to be a significant number of employers that are saying they wouldn’t hire an employee that uses marijuana,” said Evren Esen, SHRM’s director of survey programs.

Companies can maintain stricter policies in states where pot is legal because federal law, which governs most workplace rules, still considers marijuana to be a controlled substance.

Over the summer, the Colorado Supreme Court said it was legal to fire an employee for legally smoking medical marijuana while not at work.

That said, what HR managers say and do don’t always back each other up. Fewer employers are drug testing now than 5 years ago, according to the SHRM numbers. A 2011 survey of 632 HR professionals found that 55% were testing all potential employees.

A little less than half of those surveyed in the new study said their organization does pre-employment drug testing for all candidates, which just about matches testing practices nationwide.

Mountain States Employers Council, based in Denver, reported that only one in five companies in Colorado planned to make drug-testing more stringent after marijuana passed last year.

The survey found that employers are most likely to test current employees if there’s an accident or a reason to think they’re coming to work high.

Lara J. Makinen, an HR coordinator at the Denver-based Atkins, a design and engineering consulting firm, said “Some companies have stated more clearly that they reserve the right to test, letting employees know that it’s not OK to come to work under the influence.”

In states where pot has been legalized for recreational use, 39% of those surveyed have policies that single out marijuana use.

Employers might also make more drastic changes if pot use starts interfering with work life.

So far, apart from one local news story, there haven’t been reports of hordes coming to work stoned. That jibes with SHRM’s findings. Only 21 percent of employers reported more than three incidents of employees violating policy regarding marijuana use over the last year.

“It doesn’t appear to be a really major problem,” Esen said. “It doesn’t seem like employees are going out there and rampantly using marijuana in greater numbers than before.”