Switzerland
Practice Relating to Rule 20. Advance Warning
Switzerland’s Basic Military Manual (1987) states: “During every attack, commanding officers at the battalion or group level, and those of higher ranks, shall take care that the civilian population is warned if possible.”
Switzerland’s Regulation on Legal Bases for Conduct during an Engagement (2005) states:
165 The following precautionary measures must be taken into consideration when making decisions, when issuing orders and in particular when conducting military operations.
…
168 If military circumstances permit, effective advance warning must be given of attacks which may affect the civilian population.
In 2005, Switzerland withdrew its reservations to Articles 57 and 58 of the 1977 Additional Protocol I.
In 2010, in its Report on IHL and Current Armed Conflicts, Switzerland’s Federal Council stated:
Military responses to guerrilla tactics must be in conformity with the requirements of international humanitarian law. There is a consensus today that the majority of the provisions of [the 1977] Additional Protocol I apply equally to non-international conflicts through customary law. … Even if combatants blend in with the civilian population and use it as a human shield in violation of the law, it is necessary … to spare civilians as much as possible (for example by warning them in advance).

[footnotes in original omitted]