By Marc Champion

It's hard not to enjoy Boris Johnson. As much of Europe, including the U.K., turns inward and throws up fences in vain attempts to ward off a global economic storm, London's mayor is arguing for open borders and trying to poach investors from France.

Traveling in India this week, Johnson lobbied -- in his disarming, stand-up-comedian style -- for more Indian investment in London. He understands the city will thrive or wither based on its openness to immigrants and foreign businesses.

He took a swipe at a favorite target, the French, after Industry Minister Arnaud Montebourg recently accused Indian steel magnate Lakshmi Mittal of lying and blackmail over plans to close two furnaces at the Florange plant in France, and said he wanted Mittal's company out the country.

This was an extraordinary outburst. ArcelorMittal employs about 20,000 people in France, of which it plans to fire slightly more than 600. The company reported a net loss of $709 million in the third quarter amid rising overcapacity in the global steel industry. Prime Minister Francois Hollande has pledged to save the jobs and says nationalizing the Florange plant is on the table.

"Venez a Londres, mes amis!" Johnson said to his Indian hosts in video comments, inviting Mittal to move operations to the U.K. and flee the "sans-culottes" he said have taken over the French government. He was referring to the French revolutionary workers of 1789 as reincarnated -- in Johnson's view -- in Montebourg and France's current socialist government.

Johnson also attacked the U.K. government's efforts to restrict immigration, arguing -- correctly -- that immigration has benefited London's industry, universities and society ever since "a bunch of pushy Italian immigrants" (that would be the Romans), founded the city.

Life, of course, is not so simple. If Mittal left France for the U.K., he would sell and leave behind assets that would then continue to serve the French market for another steel company. The probability that he could keep that market and supply it from across the channel is approximately zero. That's why he bought the French operations in a hostile takeover in 2006. Besides, another Indian company, Tata Steel Ltd., this week said it was closing 12 sites in the U.K. at a cost of 900 jobs. Next to the U.K.'s manufacturing industry, the French one looks strong.

The immigration policies Johnson attacked are those of his own party, the Conservatives, and were rolled out because they are politically popular. Although he's routinely touted in the U.K. press as a potential challenger to Prime Minister David Cameron for the party's leadership and top job, Johnson faces an uphill task as London mayor to roll these anti-immigration policies back. Ordinary Britons are wary of arguments for openness right now, as they pay via higher taxes, steep public-spending cuts and a stagnant economy for wartime-scale debts incurred by the global finance industry based in London. Trade between India and the U.K., meanwhile, is small. It's certainly no substitute for trade with the rest of the European Union, which Johnson despises.

It's good, all the same, to have someone so articulate make the case for open borders and to speak out for an unpopular truth: namely that immigration and open borders are benefits.

(Marc Champion is a member of Bloomberg View's editorial board. Follow him on Twitter.)

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-0- Nov/28/2012 15:30 GMT