Laissez-passer and emergency passports
A laissez-passer (from the French let pass) is a travel document issued by a national government or certain international organizations, such as the United Nations, European Union, and the International Committee of the Red Cross (ICRC). A laissez-passer is often for one-way travel to the issuing country for humanitarian reasons only such as Restoring Family Links.
Some national governments issue laissez-passers to their own nationals as emergency passports. Others issue them to people who are stateless, or who are unable to obtain a passport from their own government, or whose government is not recognized by the issuing country.
One such example is the People's Republic of China, which issues the non-passport Chinese Travel Document to its nationals under certain circumstances. One such circumstance stems from a reported loss of passport while traveling or living abroad.
China issues a temporary two-year validity Travel Document in lieu of a passport to allow said citizen to complete their travels and return to China to apply for a replacement Chinese passport.
Under other circumstances such as a Chinese citizen studying or working abroad, the Chinese embassies or consulates will issue passports if requested. This Travel Document is a blue-covered passport-sized booklet clearly denoted "TRAVEL DOCUMENT" as opposed to the usual red-covered passport.
Historically, laissez-passers were commonly issued during wartime and at other periods, literally acting as a pass to allow travel to specific areas, or out of war zones or countries for various officials, diplomatic agents, other representatives, or citizens of third countries.
In these contexts, a laissez-passer would frequently include quite specific and limited freedom of movement. The form and issuing authority would be more or less standardized, depending on the circumstances.