Inter-Entity Boundary Line

The Inter-Entity Boundary Line (, ), commonly abbreviated IEBL, is the administrative line that subdivides Bosnia and Herzegovina into two entities, "Republika Srpska" and the Federation of Bosnia and Herzegovina. The total length of the Inter-Entity Boundary Line is .
History.
The present political divisions of Bosnia and Herzegovina is based on "Annex 4" of the "General Framework Agreement for Peace", also known as Dayton Agreement, concluded at the Dayton Peace Conference in November 1995, and subsequently signed in Paris on December 14, 1995. A key component of this was the delineation of the Inter-Entity Boundary Line (IEBL), to which many of the tasks listed in the other Annexes referred. 
In particular the IEBL affected the tasks of the "Military Annexes", such as the initial and immediate "Separation of Forces", the creation of an initial "Zone of Separation", the "Transfer of Areas" between the entities and the district, and the "Removal of Forces" to "Containment Areas".
During this initial "Implementation Period", enforced by NATO-led "Implementation Force" or IFOR, it was required that along the IEBL a so-called 2 km "Zone of Separation" be established, which stretched toward both entities, making a zone 4 km wide in total.
The IEBL mostly follows along the military front-lines as they were at the end of the Bosnian War (with some major adjustments, most notably in the western part of the country, and in-and-around Sarajevo).
Mapping technology.
Dayton marked the first occasion when three-dimensional satellite image technology and digital cartography was used to determine and delineate boundaries in an official treaty. Due to the speed and intensity of the negotiations (especially towards the end), a series of Inter-Entity Boundary Line commissions still needed to be held over the first 6 months of the NATO-led Implementation Force (IFOR) operation to iron out the remaining details of some of the boundaries (especially within Sarajevo). Over 40 changes to the IEBL were negotiated by the parties in meetings facilitated by the Chief of Staff HQ ARRC, Major General Michael Willcocks. These were signed off by IFOR Commander Admiral Leighton W. Smith, Jr. in July 1996.
The IEBL between Republika Srpska, the Federation of Bosnia and Herzegovina and the Brčko District is no longer controlled by the military and is not policed. There are no "Zone of Separation", or any kind of border controls and crossings. The IEBL is akin to crossing a U.S. state boundary.
Ruling of the Constitutional Court.
The Constitutional Court of Bosnia and Herzegovina has, in its first partial decision number U 5/98, ruled on the issue whether the Constitution of the Republika Srpska can use the word "border" instead of the "boundary" in its text. The Court declared:
Thus, the Constitution of the RS had to be amended, which was done with the Amendment number LXVIII, which changed the word "border" to "inter-entity line of demarcation" in the Amendment number LV on the Article 2 paragraph 2 of the Constitution of RS.
Municipalities divided by the line.
48 out of 109 municipalities were divided into two or more segments.
Legend:
At the time of the creation of the Dayton Accord, Brčko was also divided between FBiH and RS; but lately, the city was re-consolidated in the entity-neutral Brčko District, in a way to connect Tuzla to Posavina cantons in FBiH and Pelagićevo and Donji Žabar to Lopare and Bijeljina in Republika Srpska.