The 1972 International Regulations for Preventing Collisions at Sea (also known as "72 COLREGS", "COLREGS", or just "International Rules") is the set of regulations for all vessels travelling on international waters outside of established national lines of demarcation. These lines are shown on nautical charts as pink dashed lines and are labeled "COLREGS DEMARCATION LINE".
The Inland Navigational Rules Act of 1980 defines the navigation rules that apply to U.S. waters inside the COLREGS demarcation lines, including the Great Lakes and major rivers. These rules are usually referred to as the "Inland Rules".
Please note that many small harbors along the U.S. coast are considered "international waters" with regards to navigation rules because there are no COLREGS lines of demarcation for them.
The Inland Rules are almost identical to the International Rules, with only a few exceptions. The Navigation Rules booklet published by the U.S. Coast Guard lists each international rule and its corresponding inland rule on adjacent facing pages, so it is easy to compare the two.