BARCELONA, Spain — On a recent evening, two vacationing German college students, armed with addresses they had gotten off the Internet, were trying to get into one of Barcelona’s new marijuana clubs.

They were not members. But no matter. They quickly found a club near the city’s central boulevard, La Rambla, that was willing to ignore the rules, helping them choose from a dozen strains of marijuana for sale in plastic bins before letting them settle into the cushy lounge area to light up.

Forty-five minutes later, they were back on the street, smiling. “It was very nice,” said

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