The flag of Montenegro was officially adopted with the Law on the state symbols and the statehood day of Montenegro on 13 July 2004 at the proposal of the government of Montenegro. It was constitutionally sanctioned with the proclamation of the Constitution on 22 October 2007.

The flag of Montenegro is red, with the coat of arms in the middle, and golden borders. The ratio of the flag is 1:2. The coat of arms takes up ​2⁄3 of the flag's height. The middle point of the coat of arms matches the middle point of the flag. The width of the border is ​1⁄20 of the flag's proportions. Two versions of the Montenegrin flag are in use, horizontal, mostly used outdoor; and vertical, mostly used indoor.

The Law on the state symbols and the statehood day of Montenegro reached full effect the day after its publication in the Official Gazette of Montenegro. The publication occurred 12 July 2004 and the legal power of the Law occurred the day after, on 13 July 2004 – the statehood day of Montenegro.

More Info: en.m.wikipedia.org