When a pizzeria closes, the pizzeria down the block usually sees a surge in business. That principle applies to commerce in the larger North American neighborhood. Whenever the United States locks the gate on a plausible economic activity, Canadians move in and profit.

The Bush administration's hostility toward stem-cell science created opportunity in Canada. Starved of adequate federal support, American labs doing this cutting-edge science shrank or closed down, and many of their researchers moved to Canada. Between 2002 and 2007, the number of American university professors and assistants relocating to Canada jumped 27 percent, according to Canadian immigration officials. Some were stars in stem-cell research.

The Obama administration has ended that Canadian advantage by reversing the Bush policy. Canadians now fear they might suffer their own brain-drain back to the United States — and not just of Americans. European, Asian and other scientists, who went to Canada rather than the United States, may decide to head south.

A recent headline from Toronto's Globe and Mail says it all: "As U.S. emerges from Dark Age, Canada's scientific edge fades."

Hemp is a plant used to make paper, oils, textiles and other products. American farmers from George Washington on grew it. But because hemp is related to marijuana, the U.S. government outlawed its cultivation in the "50s.

Now get this: American manufacturers are free to import hemp fibers, oil and seed from other countries. For example, U.S. carmakers use hemp inside door panels and for insulation in seats.

Industrial hemp doesn't contain enough THC (the euphoric agent in marijuana) to get anyone high, but that hasn't stopped the federal Drug Enforcement Administration from sending out helicopters to scour the land for hemp plants growing wild in ditches.

The sight of waving hemp fields just across the Canadian border frustrates many American farmers. One of them, Dave Monson, a Republican, is speaker of the North Dakota House.

Monson and other farmers sued the DEA in 2007, demanding the right to plant hemp. The case was dismissed by a U.S. district court judge in Bismarck but is now before the 8th Circuit Court of Appeals, in St. Paul, Minn.

Monson told me that he tried to reason with the DEA about industrial hemp. The federal agency responded that minuscule amounts of THC could be processed out of the plants, admittedly with great effort.

"Well, why would anybody do that?" Monson asked, especially now that actual marijuana plants are freely grown in California and other states that have legalized medical pot.

"The ironic thing is that they may get medical marijuana legalized before we can get industrial hemp legalized," Monson said. The Obama administration has yet to signal a change in policy toward industrial hemp.