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.

For another 200 nautical miles beyond the contiguous zone is the ‘Exclusive Economic Zone,’ wherein the waters are technically international waters, but the nearest nation has an exclusive claim to the natural resources which lie beneath the water, such as fishing and mining rights from the ocean floor.

All of these rules pertain only to member states who sign and observe treaties recognizing these maritime laws.

The new rules come at a time of increasingly heightened tensions between China and the United States. In a bid to lay claim to the vast natural resources that lay beneath the ocean, the Chinese have aggressively expanded their presence in the South China Sea, to include the construction of artificial islands to further extend their influence.

Recent reports have indicated these man-made islands are continuing to expand their infrastructure to support military equipment, like aircraft and missiles. Satellite imagery has confirmed the addition of surface to air missile sites on the Spratly Islands, further complicating the military situation, and a potential U.S. response.