Marijuana legalization brought unexpected challenges to Colorado, and it was rarely clear what part of state government was supposed to solve them, or how.

Businesses were selling marijuana-infused, animal-shaped candy attractive to children. Residents growing pot at home were selling it illegally in other states. Growers were applying pesticides to cannabis plants even though none was specifically approved by the federal government for such use.

Enter Andrew Freedman, Colorado’s pot czar, who is bringing together the state’s bureaucracy, marijuana industry, law enforcement community, and public health advocates to fix problems no other state had faced.

Their position on marijuana is hardly the only difference between Canada's prime minister and the president-elect of the United States.

But when Justin Trudeau's government introduces legislation to legalize cannabis this spring, it could spark problems between Canada and the U.S., particularly since Donald Trump has indicated he will keep pot illegal at the federal level.

Here's a look at what could change in Canada-U.S. relations once Canadians start lighting up legally.

Border control

Len Saunders, an immigration lawyer in Blaine, Wash., predicts a boom in his business after Canada legalizes marijuana -- though it's one he has a hard time feeling happy about.

When Ohio Gov. John Kasich effectively legalized medical cannabis in Ohio, with a stroke of a pen, the state became the 25th in the U.S. to legalize a very comprehensive medical cannabis program. This week the Ohio Board of Pharmacy has rolled out several new sets of rules for the evolving program.  Finally clearing the smoke with Ohio’s medical cannabis program with some sort of focus in rules now proposed for cultivators, doctors who recommend it for patients, and for dispensaries.

Critical op-ed argues that if the industry is actually so nervous about Jeff Sessions, it should oppose his appointment.

On Friday, avid cannabis journalist Alex Halperin published a scathing critique of the pot industry’s post-election posture at Slate. He contends that despite the legal weed sector’s professed anxiety and handwringing over President-elect Donald Trump’s nomination of Sen. Jeff Sessions for U.S. Attorney General, it’s not really doing anything to try and stop it, even though the ballooning industry now has more clout than ever with the political establishment.

Nevada’s cannabis industry wants to be tested.

Hoping to avoid the pitfalls seen in other states that have legalized marijuana, several in Nevada’s marijuana industry want the state’s stringent testing of medical marijuana products to be carried over to the recreational market. Doing so is essential to protecting the consumers, they say, as well as the industry.

“We need to make sure this product is safe. And the only way to make sure it’s safe is to test it,” said Kelly Zaug, lab manager at DV Labs in Las Vegas, during a Las Vegas Medical Marijuana Association panel discussion Thursday.

Puff, Pass & Paint, the nation's first cannabis-friendly art class, adds locations in Las Vegas and California as additional states legalize recreationally.

"Puff, Pass & Paint", the nation's first cannabis-friendly art class, continues to expand nationally with recreational legalization in California, Nevada, Massachusetts, and Maine. Based in Denver, the smokey art session has also expanded to Portland, Seattle, and Washington DC, with dates available in San Francisco and Las Vegas starting January of 2017. The company will add additional events and locations as legalization allows, with Boston, Portland, ME, San Diego, Los Angeles, and Orange County, CA scheduled for immediate expansion as well. 

On Wednesday, Steven Ognibene had to take the day off from work.

The Rochester surgeon needed to drive three hours to Binghamton because the type of medical marijuana that could help his 11-year-old son, Vincent, wasn’t available locally. It was, though, available at a dispensary in Johnson City, Broome County.

The trip illustrates the obstacles some patients and their families are facing nearly one year after New York allowed for the use of medical marijuana in non-smokable forms for certain conditions.

As California prepares for the era of legal marijuana, Israel is emerging as a potential overseas partner in new cannabis-related enterprises.

As a report in Sunday’s New York Times notes, Israel has been a leader in medical research into the benefits of marijuana, and is currently conducing more clinical trials than the United States, which one Israeli expert called “ridiculous.” With California and other jurisdictions legalizing marijuana cultivation, Israel is moving to expand it abroad.

Colorado’s Health Department announced Tuesday the state will provide $2.35 million for research on the effects of marijuana, with most of the money aiding in two studies analyzing the impact marijuana has on driving, Denver Post reported.

Another hurdle has been cleared for supporters of legalizing recreational marijuana in Maine.

On Saturday, opponents of the ballot measure legalizing pot conceded to the Yes on 1 campaign. That followed a recount of somewhere between a third and a fourth of all ballots cast in Maine on Election Day.

A lawyer for the No on 1 campaign said it became clear this past week that the results of November's election wouldn't be changed by the recount. He also said many towns and cities in Maine may still consider banning recreational pot use.