|“||Samus, you shouldn't have done that. You ignored your orders. You may have to pay a price for that quite soon...||„|
The Restricted Laboratory was located in the Restricted Zone of the Biologic Space Laboratories research station. It is found in a separate area at the bottom of the Main Deck and is connected to Sector 1 (SRX) and Sector 6 (NOC); the lab was designed to be detached in case of an emergency or a security breach. The Galactic Federation built it to house the captive-bred Metroids that they created from the DNA of the last Metroid.
When Samus Aran discovered the entrance to the Restricted Lab in Sector 6, she triggered an alarm that repeated the phrase "Warning: No entry without authorization". Unable to enter, Samus retraced her steps and promptly ran into the B.O.X. that she had encountered in Sector 3. After defeating it, Samus absorbed the Core-X left behind and regained the Wave Beam ability. With the Wave Beam, she was able to break into the Restricted Lab opening a shutter from the opposite side of its opening mechanism.
Inside the lab was a massive tube filled with several Infant Metroids floating about; in the next room, a mature Larval Metroid, an Alpha Metroid, a Gamma Metroid, and a Zeta Metroid were being kept in large green tubes that resembled the Baby's container on Ceres Space Colony. While Samus was looking at these in shock, she realized the Galactic Federation had lied to her about its intentions with the Metroids; instead of exterminating them, they were researching and breeding these creatures.
As Samus continued to explore the laboratory, an SA-X that had been tracking her entered the Restricted Laboratory and opened fire on the Infant Metroids in an attempt to destroy its natural enemy. Its plan backfired when the freed Metroids overwhelmed the SA-X, but the damage was done; the lab's security had been breached, and emergency fail-safes immediately took effect. A 1-minute Countdown to the detachment of the entire Restricted Lab began. Samus was able to escape before the lab detached from the B.S.L. research station and self-destructed, killing the SA-X and what were apparently the last living Metroids in existence. It is possible, however, that there are still Metroids being kept by either the Galactic Federation or Space Pirates somewhere. At least one Metroid escaped the destruction and quickly advanced to the Omega Metroid stage, but it was later killed by Samus when she was escaping the station.
Incidentally, the only actual Metroids in Metroid Fusion (aside from the escapee and Samus herself) are found in the Restricted Lab, and they do not actually damage Samus; they do fly around in a frenzy as Samus attempts to escape, and they can interfere with her attempts to Space Jump up the escape shaft. The most likely reason that the Metroids do not attack Samus is because they see her as one of them due to the Metroid DNA in her body (the Omega Metroid is an exception).
Unlike the Bottle Ship's Project Metroid Warriors, which was designed to use the creatures as bioweapons, the breeding program in the BSL Station was for peaceful purposes only, according to the computerized Adam. Samus was scolded by the computer for being partly responsible of the Restricted Laboratory's destruction.
- Parts of Fusion are inspired by the film Alien Resurrection; an example being the female protagonist being reborn as a hybrid of herself and both series' alien species. In Resurrection, Ellen Ripley, the protagonist of the Alien series, mourns when she kills her preceding seven clones by incinerating the lab, and at the end of the film when she flushes the Newborn out into the vacuum of space through a broken window pane. Unlike Ripley, Samus is never seen to have mourned the destruction of the Metroids in the Restricted Lab or her killing the Omega Metroid, even though she possessed Metroid DNA at the time.
- The Restricted Laboratory contains many similarities to the prequel's Sector Zero; Metroids were bred, both sections detach via fail-safe protocols if they take enough damage, both were detached by someone other than Samus, and both stations were successfully destroyed.
- It is possible that a Queen Metroid could have been bred in the Restricted Laboratory as Samus encountered one during the events of Metroid: Other M. However, it was also said that the Federation had never expected a Metroid to grow to such lengths in so little time, and the methods used by MB to grow a Queen outside of the environment of SR388 were never revealed to anyone. Also, when Adam opens up and reveals everything to Samus after the destruction of the Restricted Laboratory, he fails to mention any Queen onboard the BSL. Specimen tubes extend into the background, possibly indicating that a Queen might have been produced but was not seen ingame despite Adam failing to mention it, and gave birth to all specimens.