This is the relevant section from the wiki:

Many jurisdictions have enacted regulations relating to the disposal of human bodies. Although it may be entirely legal to bury a deceased family member, the law may restrict the locations in which this activity is allowed, in some cases expressly limiting burials to property controlled by specific, licensed institutions. Furthermore, in many places, failure to properly dispose of a body is a crime. In some places, it is also a crime to fail to report a death, and to fail to report the disposal of the body.[37]

From your link:

Having a grave too close to a water source is either not wise or not legal. It also may not be permitted to have a gravesite within a certain distance of a building or your property line. These are called setbacks, and setback laws are different for each state. Often, setback rules make it all but impossible to put a grave in someone’s urban or suburban property without breaking the law.

I’d be interested in how widespread the legality is practically, because (reasonably) everything I looked at said to check local laws, but I can understand why that’s not included exhaustively. My family tried to in a rural area of a non rural state where the sources say it’s allowed, but the setbacks made it practically impossible- watershed areas are larger than you would expect, even without visible bodies of water nearby.