With the world more and more concerned about energy and metals shortages, and the likes of Rio Tinto (NYSE:RTP) becoming the apple of nearly everyone's eye, authorities in Moscow have effectively erected a huge "hands off" sign for foreigners who might have an interest in Russian resources companies.

In an effort to keep overseas investors from building stakes in its extractive industries, Russia has established new rules limiting the percentage of a company's shares that can be sold abroad. Effective late next week, Russian companies involved in geological exploration will be permitted to sell only up to 5% of their shares overseas. That restriction rises to 25% for companies in strategic industries or involved in national security. For all other companies, the limit is 30%, down from the prior 35%.

The rules exempt companies currently listed abroad. So it appears that if you own shares in, say, Mechel (NYSE:MTL), the big Moscow-based mining and metals company, you've been grandfathered.

Of course, these rules are just formalizing what the likes of Royal Dutch Shell (NYSE:RDS-A) and BP (NYSE:BP) have learned the hard way: that Russian authorities aren't inclined to share their country's natural resources with the rest of the world. The two European-based oil companies developed assets in Russia, only to have local authorities begin playing hardball and, in Shell's case, force a sale of its assets to Gazprom (OTC BB: OGZPY.PK) at a below-market price.

Whether it involves energy or mining resources, the world has become progressively more concerned about shortages and more subject to the sharp elbows of resource nationalism. The first concern clearly led Alcoa (NYSE:AA) and Aluminum Corp. of China (NYSE:ACH) -- Chinalco -- to team up for a stake in Rio Tinto, the big London-based mining company, earlier this year.

But in addition to turning our vaunted globalization into a sort of one-way semi-globalization, while reducing opportunities for outsiders to participate in the expanding Russian economy, it seems that authorities in Moscow are unwittingly providing another key message for Foolish investors. On the one hand, there's a case to be made for putting some of your hard-earned bucks into Gazprom, for example. But on the other, with Russian authorities demonstrating almost daily that they failed to learn sharing on the playground, I'd also urge you to be very, very circumspect about investments in that country.

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