Starting Monday, recreational marijuana will be legal all along the continental West Coast.

That's when California falls in line with Oregon, Washington and Nevada, where voters legalized retail pot sales over the past few years as use of cannabis has become more socially acceptable across the U.S.

In October, a Gallup poll showed a record-breaking 64 percent of Americans support marijuana legalization. Despite increasing popularity among citizens, however, nationwide legalization doesn't appear to have anywhere near enough votes to pass in Congress.

More:Legal pot dealers find home: Oregon's Cannabis Coast

There just aren't enough Republicans who are true Libertarians, like U.S. Sen. Rand Paul, R-Kentucky, to vote in favor of legalizing marijuana, said Jim Moore, director of the Tom McCall Center for Policy Innovation at Pacific University in Forest Grove.

For real change, attitudes would have to shift in red states like Arizona and the Dakotas, he said.

Moore said what's happening now is "like a slow-motion end of Prohibition." Instead of a constitutional amendment ending the ban on alcohol, a growing number of states are legalizing marijuana on their own.

One path to national legalization could see congressional lawmakers from weed-legal states overturning the federal ban — or, as with same-sex marriage, people may say the tide has turned and call for state and federal laws to reflect the change, Moore said.

Gallup pollsters likened changing attitudes toward marijuana to changing opinions on same-sex marriage, which the U.S. Supreme Court declared legal in 2015.

For now, Moore says the wave of Washington, Oregon and California all legalizing marijuana is viewed nationally as "That darn blue wall."

But California's shift could be a game changer. Its economy is so large that where the Golden State goes, the country tends to follow, he said.

Still, the concerns of opponents to legalized marijuana aren't going away. They include worry that pot is a gateway to more deadly drugs, including heroin and meth, and that the proliferation of weed will lead to more children getting their hands on it, even as that remains strictly illegal.

"We are commercializing and normalizing essentially a new tobacco industry that targets kids and also targets adults to make them lifelong users," said Kevin Sabet, president of anti-legalization group Smart Approaches to Marijuana.

"Most parents don't want their kids to use," he said. "In fact, I've never heard a parent or a teacher say, you know, 'If only our kids used more marijuana, they'd be better off.' It's the opposite."

You can still get arrested

West Coast residents and tourists who plan to partake of legal pot should know a few rules to keep themselves out of trouble:

Don't cross state lines with weed: Despite efforts in Congress to decriminalize marijuana across the U.S., it remains illegal under federal law.

A bill introduced this August and cosponsored by two Democratic lawmakers, including U.S. Sen. Ron Wyden of Oregon, would remove pot from the federal list of controlled substances.

More:Sen. Ron Wyden cosponsors bill to legalize marijuana across U.S.

But Wade Sparks, spokesman for the Drug Enforcement Administration, stresses that people who move marijuana across state lines could open themselves to prosecution.

Sparks worked as a field agent in California and Texas before moving to Washington, D.C. He and other DEA officials used to travel from Texas to California to arrest people mailing medical marijuana across the country and put them before a federal judge — something he says still happens today.

They also would pull over drivers in Texas with pot in their cars, he said, and patients would show their out-of-state medical marijuana cards. "That is not considered a defense," he said.

Oregon and Washington officials also say marijuana must remain in-state.

Don't smoke and drive: Authorities in California are expecting a rise in DUI arrests from drivers using cannabis.

It's still illegal to drive and use weed, just like drinking and driving. Same goes for Oregon, Washington and Nevada.

Californian authorities also say it's illegal to have an open container of marijuana while operating a vehicle.

Sacramento allocated $3 million to the California Highway Patrol to train local and state law enforcement officers on how to respond to signs of impairment from marijuana.

The highway patrol, whose main concern is ensuring motorist safety, will be looking for impaired drivers around California, said CHP spokesman Mike Martis, Jr.

Don't consume in public places: Oregon law prohibits using recreational marijuana in public spaces, such as on sidewalks and in parks.

It's the same in California. Martis also says that while it's legal to use marijuana on private property, property owners and landlords can bar use of the drug. In Oregon, the public cannot be able to view marijuana use from a public street or sidewalk, even if the consumption is taking place on private property.

The legal age remains the same: In all four states, only people 21 and older are allowed to buy and use recreational marijuana.

And customers can only buy from retailers licensed by state regulators. Black market transactions are illegal and can be prosecuted.

Selling marijuana to minors can result in license suspensions and hefty fines for retailers.

Earlier this month, the Oregon Liquor Control Commission, which regulates recreational marijuana sales, sent inspectors to 20 central Oregon pot retailers to make sure they weren't selling to minors.

"This is part of our stepped up compliance and enforcement activity," Steve Marks, the agency's executive director, said in a statement.

Inspectors went with underage volunteers to retailers in Bend and La Pine. The minors carried their own ID cards that show they're underage. The point of the exercise is to see if workers are checking ages when people enter and try to buy marijuana.

Every retailer passed the test.

Reach staff reporter Jonathan Bach by email at jbach@statesmanjournal.com or by phone at 503-399-6714.