The CIB was established by Executive Order in 1942 and made retroactive to the beginning of the war. Only officers and enlisted personnel of the infantry, in the rank of Colonel and below, were eligible. Officers of other arms were eligible when assigned to the command of infantry units but enlisted personnel were required to be infantry MOS. Officially, an individual must have "subsequent to 6 December 1941 . . . satisfactorily performed duty while assigned or attached as a member of an infantry unit of brigade, regimental or smaller size during any period such unit was engaged in active ground combat." Defining "satisfactorily performed duty" was left to the descretion of commanders - usually regimental commanders - in the field.
The general requirement of thirty days (consecutive or cumulative) service with an infantry unit was also a policy established by commanders in the field. The badge, when granted in accordance with the above, was authorized in General Orders and award was effectuated by an entry in the individual's 201 File or SRB.
In some relatively few cases, the badge was awarded for "an individual act of gallantry in action of a lesser degree than that sufficient to warrant an award of the Silver Star." This policy was discontinued when the Bronze Star was established. Such "valor awards" were announced in Special Orders which often included a brief, general account of the deed for which the individual had been cited.
The Bronze Star was created by Executive Order 9419 of 4 February 1944 and made retroactive to 7 December 1941. Individuals who had received VALOR AWARDS of the CIB prior to this were eligible TO BE CONSIDERED for the Bronze Star (issuance of the decoration was to have been based on case-by-case review of each individual valor award of the badge). This was to have been similar to the prodecure established in 1933 for the issuance of Silver Star decorations to replace Silver Star Citation Certificates awarded during World War I and earlier but the process broke down and the procedure went awry.
For about fifty years now, individuals have been issued Bronze Star decorations literally on demand and solely on the basis of possession of a CIB (very much like Medals of Honor were issued in the late 1800's and early Twentieth Century). As stated previously, this is - and always has been - a result of misinterpretation and misapplication of the policy of in-kind issuance of Bronze Star decorations in recognition of valor awards of the CIB. Period.