Taken into consideration the length of the period of the Middle Ages, I reckon that something similar could have been found inside the Germanic Law shared by the Franks, Lombards and North Germanic peoples of Scandinavia. Here, the term "law" must be taken broadly as it mostly comprised of customs and traits which were very specific to their own culture, and sometimes clashed with previous and different judicial practices (for example, Italy).

Within the codification of Lombard laws under the Lombard king of Italy Rothari in 643, and in the Salic Law of 507-511 concerning the Franks, we see two ways to settle matters of honour between two individuals which could have been of different rank from one another, by either a "regulated" blood feud, or with the payment of a compensation, known as wergild. For example, the first one states that if, between two freemen, one is wounded in the head and a piece of broken bone flies away, it must be paid 12 solidii (silver coins, each approximately 1/240th of a lira weighing roughly 500 g) for each, but only if it makes sound if dropped on a shield from twelve feet of height. Similarly, if a man has a thumb or index cut off, a full sixth of the price of an overall person must be paid as compensation. It is also written that for a missing tooth ("one of those which can be seen while laughing"), 16 solidii must be paid and half for those in back of the mouth. If a man is killed, a price must be brokered between the two parties involved.
The Salic Law specifies the compensations instead. A Frankish freeman was worth 300 solidii, a Frankish antrustio, a king's sworn man, 600 must be paid. The Edictum Rothari implies that slaves as well had a worth, even though Roman ones were less worth than Germanic ones. All these laws were in place in order to safeguard a man's honour, either through blood price or conventional price, which was just as good since it meant having received a compensation to match the honour of the slain's family, ending the feud. Of course, breaking this custom occurred and was heavily frowned upon.

Later into the Middle Ages, in Center and Northern Italy during the 1200s and 1300s, blood feuds between families still occur, as we're told by many chroniclers of the era. What we are told is also that monetary compensation has fallen out of favour, but slaying a rival family member to avenge a murdered relative was a thing. Dante Alighieri tells about one of his ancestors he claims to meet while traveling through Hell, Geri del Bello, who was killed between 1280 and 1300 and, as of Dante's journey, had not yet been avenged (let's note that this man was tried for assault in Prato in 1280), thing which would occur some time later as we know of a formal peace deal between the Alighieri and Sacchetti (the feuding family responsible for this murder) in 1342.
Additionally, Dante's master, Brunetto Latini, recounts several ways in which one should behave if in a feud with someone, regardless of its status he claims, as every man can muster help for a vengeance. Thus he suggests always going around armed and in company, never travel during nighttime and never think such an offence can be deemed too old to be exacted justice for. This last part we are aware of due to another source, Salimbene of Parma, a Franciscan monk from the city of Parma who states in his Chronica that a feud "25 years old is still considered worthy and fresh in Parma. And I am from Parma".

To sum it up, given the diverse nature of juridical systems existing in Europe during the Middle Ages, a clear and comprehensive line cannot be drawn for sure, but we can guess with moderate consideration that outright murdering someone of lesser condition was not fully sanctioned by law in the vast majority of cases.