China's new border control rules take effect today, and Taiwan's government says the danger of being blocked from leaving the country has gone up sharply — bad news for Taiwanese business people working in China.

• The rules turn informal border practices into written law and hand officials much wider power to decide who can leave.
• Enforcement authority now reaches down to county level, where local officials may over-enforce rather than risk missing someone.
• Taiwanese business owners, managers, and workers in high-tech and new energy are seen as the most exposed groups.
• Officials can be stopped from leaving over suspected export or technology violations, without any conviction, and may not be told the reason or given a way to appeal.
• Border officers can demand documents, data, and electronic records, which Taiwan reads as a push to control both people and technology ahead of a wider tech fight with the US.

Outlook: Expect Taipei to keep warning citizens against travel to China, and more caution from Taiwanese companies about sending staff across the strait.