It is almost a decade since China joined the World Trade Organization. Back then, China imported "global order": it absorbed pre-existing, mainly U.S.-designed policies, rules and institutions. It acted rather like a small or medium-sized economy that could only adapt to the international terms of trade. Now China is one of the Big Three, alongside the U.S. and European Union. It is the world's second-largest economy and its leading exporter of goods. It is also the biggest post-crisis contributor to global growth.

In line with its growing economic size, Beijing wants to influence international prices and shape global rules. But that will require significant changes in the ways Beijing thinks about economic policy, and Beijing has resisted those changes to date. This creates uncertainty and instability for China and the rest of the world, and has implications for other leaders looking to China to play a constructive role in global economic matters.

Global trade issues best reveal China's policy shift, and also its policy dilemma. China's membership of the WTO has been a resounding success. Access to the WTO's rules-based system and dispute-resolution process has defused manifold tensions and smoothed China's rapid integration into the global economy. Beijing also has negotiated bilateral or regional free-trade agreements such as the one with the Association of Southeast Asian Nations.

But China also has been a conspicuously passive and marginal player in the Doha Round of talks to further liberalize global trade. Its default position is still to react, leaving other big players to take initiatives. And its FTAs tend to be fairly weak. Whereas, for instance, South Korea's FTAs with the U.S. and EU represent comprehensive liberalization in trade between major partners, Beijing's pact with Asean only eliminates tariffs; it hardly, if at all, tackles regulatory barriers to trade in goods and services, investment and public procurement. Other Chinese FTAs, such as its agreement with Pakistan, don't even eliminate most tariffs.

Meanwhile, China's historic opening to the world economy has stalled since about 2006. There has been paltry unilateral liberalization beyond China's WTO commitments. Anti-liberalization interests—some ministries, regulatory agencies and resurgent state-owned enterprises (SOEs)—have grown more powerful. Despite, or perhaps because of, China's growing clout, it is unwilling to open markets unilaterally and haggles hard over reciprocal concessions.

Beijing's stalled liberalization is also of a piece with greater industrial-policy intervention, aimed to promote a core of about 50 SOEs, mainly in "strategic" manufacturing and resource-based sectors, and a handful of state-owned banks that dominate the financial system. China's response to the global financial crisis—a supercharged fiscal and monetary stimulus—bolstered the public sector and state power at the expense of the far-less-subsidized private sector. Beijing's frequent recourse to command-and-control mechanisms such as price controls to fight inflation makes market reform harder.

Protectionist trade policy and dirigiste industrial policy meet at several junctions. Export restrictions—most conspicuously on rare-earth metals—have increased. Tax incentives, subsidies and price controls, as well as administrative "guidance" on investment decisions, are used to favor domestic goods over imports. China-specific standards, such as on third-generation mobile phones, can create high compliance costs for foreign enterprises. Services barriers, notably in financial and telecommunication services, have come down very slowly, if at all.

Foreign-investment restrictions have been tightened in a range of sectors where SOEs operate, such as iron and steel, petrochemicals, coal, biofuels, news websites, audiovisual and Internet services. Discriminatory government procurement, in the guise of promoting "indigenous innovation," favors domestic companies. Joint-venture and technology-transfer requirements on foreign companies promote national champions in high-speed rail, electric cars and renewable-energy sectors. Finally, "investment nationalism" extends to China's Go Out policy: Resource-based SOEs in particular are buying up foreign assets with cheap capital provided by state-owned banks.

The problem is that this policy mix is incompatible with global economic leadership at a time when China has little choice but to become a global leader. Beijing can't expect its trading partners to accept indefinitely a flood of Chinese exports without opening its own market to their goods. Hence it is in China's own interests to restrain industrial-policy activism and its protectionist spillover. And it should proceed with "WTO-plus" reforms that move beyond the letter of its accession commitments. It could further reduce applied import tariffs, especially on industrial goods. It should reverse export controls on raw materials and agricultural commodities.

China's more substantial challenge is to tackle high trade-related domestic regulatory barriers in goods, services, investment and public procurement. These measures should be hitched firmly to domestic reforms to improve the business climate and to "rebalance" the economy—to make it more consumption- and less investment-oriented, with more freedom for the private sector and less public-sector control.

Most of this wish list is not on Beijing's agenda. Leaders are not minded to curtail industrial policy and proceed with reforms beyond their WTO commitments. The latter would mean not merely liberalizing product markets but also reforming highly controlled markets for factors of production like land and capital and for energy inputs like oil, water and electricity. Those lie at the heart of domestic economics and politics. The reforms China most needs now cut to the core of the Communist Party-government-public sector nexus and its grip on power. It is unlikely to happen soon.

The story is not necessarily as grim as might at first appear. Earlier liberalization has left China so deeply integrated into global supply chains that it can't afford to move too far backward on reforms, and Beijing increasingly can't afford to stand still either as it endeavors to deliver steadily rising prosperity. But until it finds a way to break this impasse, China will be limited in its ability to exercise meaningful global leadership. This fact calls for some humility from Chinese leaders who otherwise appear increasingly assertive on the world stage, and for realism from foreign leaders who wish China would exercise a greater leadership role at international forums like the International Monetary Fund, the WTO and the G-20.