China is introducing significant new measures for foreign vessels traveling through its territorial waters.

While that would normally be no cause for alarm, the Chinese are seeking to apply these rules to vast stretches of the South China Sea it has independently laid claim to, in direct conflict with the wishes of its neighbors and the United States.

According to the new rules, any foreign vessel would have to first seek permission to enter Chinese waters, and report to their maritime authority. Submarines would have to surface and fly their national flag.

The issue of maritime law is a somewhat tricky one. In general, territorial waters exclusive to any nation lay within 12 nautical miles of shore. For another 12 nautical miles, there lays what is referred to as a contiguous zone, where that nation still holds authority to set laws and regulates travel.