Under the terms of Sabah and Sarawak's entry into Malaysia, both states retain a certain degree of state-level control of their borders. Malaysian citizens from Peninsular Malaysia (West Malaysia) cannot work legally in Malaysian Borneo (East Malaysia) without special permits, and tourists travelling within Malaysia must go through passport control and have their passports stamped whenever they:

Arrive in Sabah or Sarawak from Peninsular Malaysia or the federal district of Pulau Labuan.

Exit Sabah or Sarawak on their way to Peninsular Malaysia or Pulau Labuan.

Travel between Sabah and Sarawak.

Note: When you enter Sabah or Sarawak from another part of Malaysia, your new visa stamp will be valid only for the remainder of the period left on your original Malaysian visa.