President Barack Obama’s trip to Myanmar in November—the first ever by a sitting president—wasn’t just a state visit. It was an endorsement of the steps that the country’s leaders have taken to open Myanmar to the world following 60 years of military rule.

Over the past two years Myanmar has enacted a number of reforms, including the release of many political prisoners, the relaxation of media censorship, and efforts to fight corruption. Equally important, the country has moved quickly to rev up its economy, and Obama’s visit served as a vote of confidence for Western companies eager to enter a market of 60 million people strategically located between China and India.

So, too, did Myanmar’s passage of a new foreign investment law just weeks before Obama touched down. Drafts of the bill had gone back and forth between the two houses of parliament for the better part of a year, with President Thein Sein and other supporters of reform fighting to keep the law investor-friendly. They won out, as provisions were made to remove most foreign ownership restrictions, including one that would have required minimum investments of at least $5 million.

Now, according to some observers, investors have the sign they need to begin moving into Myanmar. “They were all waiting for a positive step or indication from this law, and they all feel they have it,” says James Finch, a partner in the Yangon office of legal consultancy DFDL. “Many are going forward.”

International companies have been eyeing Myanmar since the suspension of U.S. and European Union sanctions against the country last year. Already some of the world’s best-known brands, General Electric Company and The Coca-Cola Company among them, have made preliminary moves into the country. Even more promising is what the world’s major oil and gas companies predict will be a vast store of natural resource wealth. That still largely untapped wealth is expected to become the country’s key economic driver going forward.

But while international law firms are also eyeing Myanmar—hoping to lock up some returns of their own—they say it’s still too early to commit much in the way of resources, much less contemplate a full-scale launch. “The country just opened,” says Chirachai Okanurak, Bangkok managing partner for Baker & Mc­Kenzie. “It’ll take time.”

Baker & McKenzie, Allen & Overy, Mayer Brown JSM, Herbert Smith, Fulbright & Jaworski, Baker Botts, and Rajah & Tann have all begun to serve clients interested in Myanmar, but none have set up an in-country office yet. And so far only Baker & McKenzie has hired a Myanmar-qualified lawyer, Saw Yu Win, who joined the firm’s Bangkok office in August.

There are several reasons for caution, as Finch and others note. For one thing, the foreign investment bill that President Sein signed was largely a framework for a law, and some of its specific provisions won’t be finalized until the end of January. The government is still working out the implementing regulations, and therefore a number of uncertainties remain. Not the least of which is the extent to which foreign companies will be restricted from sectors such as manufacturing, services, agricultural livestock, and fisheries, according to an Allen & Overy report.

“I think a lot of clients are just trying to absorb what’s been passed and what hasn’t,” says Simon Makinson, managing partner of Allen & Overy’s Bangkok office. “The general sort of view is that [the latest version of the foreign investment law] is better than the previous version, but no one knows what the final version is going to look like.”

Foreign investors will also have to be careful about whom they transact business with. U.S. sanctions still apply to Myanmar’s military and to businesses owned by it. Moreover, many local tycoons who became wealthy through cooperation with the junta are on the U.S. Department of the Treasury’s blacklist of “specially designated nationals” with whom Americans are barred from doing business. In April, Reuters profiled one such blacklisted tycoon, Tay Za, pointing out how hard it was for foreigners to avoid dealing with him and his ilk.

The pervasive cronyism in Myanmar has made it one of the most corrupt places on earth. It ranked 180th out of 182 countries on Transparency International’s 2011 corruption perceptions index. Only North Korea and Somalia are ranked lower for perceived corruption.

But if there is a reason to rush in, it’s Myanmar’s potential as an oil and gas producer. Last month an Asian Development Bank report put the country’s proven reserves of natural gas at 7.8 trillion cubic feet, and its reserves of oil at 2.1 billion barrels. There’s an assumption by insiders that more remains to be discovered, and international oil companies have been lining up for the right to find it. “This is one of the countries in the world that still has undeveloped fields that can still move the dial on big oil and gas companies,” says Ben Smith, a Hong Kong partner with Fulbright & Jaworski.

Still, the energy sector is hardly immune to the issues that plague the rest of the Myanmar economy. According to Reuters, a tender of onshore and offshore oil exploration blocks planned for September was postponed after a number of Western companies raised questions about the transparency of their potential counterparty, state-owned Myanma Oil and Gas Enterprise (MOGE). Lawyers in the region say the Western companies may have been influenced by activists, such as Nobel Peace Prize winner Aung San Suu Kyi, who have called for foreign companies to avoid doing business with MOGE, which has close ties to the Myanmar military.

Andrew MacGeoch, Hong Kong partner at Mayer Brown JSM, says the way forward in Myanmar will not be easy. The country, he says, is “still going to have its ups and downs, bumps and bruises along the way.” He likens the situation to that of Vietnam in the 1990s; others point to China in the 1980s or Mongolia over the past few years.

One advantage that Myanmar may have over those other jurisdictions is the common law legal system left behind by the country’s British colonial rulers when they departed over 60 years ago. But the years of military rule left gaps in the law and the training of lawyers, so there are currently very few local lawyers capable of handling international transactions. “There are a couple of good firms, but the pool isn’t particularly deep,” Herbert Smith Freehills partner Richard Nelson says. Nelson, who heads his firm’s Southeast Asia energy practice in Singapore, points to Myanmar Legal Services and regional tax and legal consultancy DFDL as a couple of the standouts.

An update of Myanmar’s laws could take many forms, and could be influenced by the experience of other developing countries in the region, as well as international bodies like the World Bank and Asian Development Bank. But, given Myanmar’s host of issues, MacGeoch is not expecting things to move fast. “The time frame for doing it will be much longer than most people expect,” he says.