Switzerland
Practice Relating to Rule 17. Choice of Means and Methods of Warfare
Switzerland’s Regulation on Legal Bases for Conduct during an Engagement (2005) states:
12.5 Precautionary measures
165 The following precautionary measures must be taken into consideration when making decisions, when issuing orders and in particular when conducting military operations.
166 Anyone who attacks:
…
2 must take all required precautions when choosing the means and methods of attack with a view to limiting maximally loss, injury and damage among the civilian population and its property.

[emphasis in original]
In 2005, Switzerland withdrew its reservations to Articles 57 and 58 of the 1977 Additional Protocol I.