|“||Warning. No entry without authorization.||„|
The first time Samus comes here, the PA announces that she cannot enter unless permitted. This zone has all of the Metroids located in it until the Restricted Laboratory is ejected out of the station.
The only parts left of this zone after the destruction of the lab are a few rooms connecting to Sector 6 and Sector 1 (SRX). There is a way to get a Power Bomb Tank by Shinesparking into the Speed Booster Blocks in the dead end room towards the Sector 6 entrance.
The rooms of the Restricted Zone bear a slight resemblance to some of the rooms seen within the Ceres Space Colony. As Metroid research was being conducted on both Ceres Space Colony and within the Restricted Zone, it is quite possible the Restricted Zone was build under a similar design as Ceres.
The theme that plays when Samus first enters the Restricted Zone from Sector 6 (NOC) is the BSL Control Station. This theme is shared with the Operations Deck and may have meant to resemble the ambience theme that plays when Samus first explores the Ceres Space Colony.
The eerie theme that plays when Samus first discovers the Restricted Laboratory is titled Environmental Sound (Disquieting) in the Metroid Prime & Fusion Original Soundtracks.
- All doors in this Zone are Level 4 security doors.
- Though Samus enters the Restricted Zone through Sector 6 and exits to Sector 1, the map of the Zone itself is a part of the Main Deck map. Therefore, strictly speaking, the Restricted Zone is a part of the Main Deck and not of Sector 1 or Sector 6.
- When using Debug Menu to sequence break into the Restricted Laboratory, the Restricted Laboratory's rooms play the Main Deck soundtrack by default, further signifying that the Restricted Zone is a part of the Main Deck.
- The background of the first room of this area says Level-X on it. This is likely an alternate name for the area.
- The Power Bomb Expansion does not appear until after the Restricted Laboratory has been detached (which can be seen via Debug Movement). Furthermore, the weight blocking access to the lower side of the tunnel leading to the Expansion strangely also blocks the Pit Blocks and its above surrounding area near and below the weight object as well.
- Quite strangely, despite there being no door present at the top-left corner of the Air Lock Hallway area, there is still a loading plane for it seen using debug features to clip out of bounds (this can be seen in both pre and post crash versions of this room, the latter until the post-crash map is reloaded). The invisible area loads to the top-right area of the destroyed Restricted Laboratory.
- Even more strangely, during the event flag where the SA-X attacks the Restricted Laboratory, the doors inside the Air Lock Hallway are programmed to be sealed off save for the door leading to the Navigation Room. This is not normally seen due to Samus being completely locked in the Lab during this flag, but if Samus enters the Hallway during this time and not through the intended exit (using Debug movement), the invisible loading area in the Hallway leading to the Restricted Laboratory reveals part of a door in its place (likely the locked door but blocked visually by the terrain).
- In earlier prototypes of Metroid Fusion, there exists an unused sound file next to the other sets of sound files concerning the Restricted Zone. This unused file is a line spoken by the BSL computer security, saying: "Unauthorized Entry". It is fairly possible this sound file would have played once Samus opened and passed through the sealed shutter into the Restricted Zone.