Keeping Kings in Check 51Moreover, Innocent was well aware that his pronouncement would not be
self- executing. Without the support of major powers such as the kings of
En gland and France, as well as of prominent subjects of Frederick, it would
be a mere empty gesture. Predictably enough, Frederick reacted to the news
of his deposition with outrage and contempt. He vowed that neither the pope
nor any church council could take his crown from him without a war. An
armed struggle duly proceeded between Frederick and the various contenders
for the crown (who had papal support). In the end, Frederick was defeated,
and the Hohenstaufen dynasty came to an end.
Th is story provides some interesting insights into medieval ways of
thought and action— as well as into key aspects of international law. Perhaps
the most distinctive feature of the Eu ro pe an Middle Ages was the power
of the papacy— a monarchy with a transnational reach, but also with a fun-
damentally spiritual, rather than material, nature. Th e Catholic Church
certainly did not lack for earthly possessions. It possessed abundant lands
and great fi nancial might. It even, from time to time, raised armies to fi ght
its various causes (as Innocent IV, for example, did in the confl ict against
Frederick). But these various material resources were— at least in princi-
ple— in the ser vice of high ideals rather than of grubby power politics. Th e
ideals included, of course, the doctrines of the Catholic Church (heresy was
among the accusations against Frederick II). But they encompassed the rules
of natural law as well, which were an important part of medieval Eu rope’s
inheritance from the ancient world.
Th e signifi cance of natural law for the development of international law
can hardly be overstated. In a nutshell, it was the idea that there is a body of
law above and beyond that of state governments. More than that, though, it
was the notion that this law actually constrains governments themselves,
just as it constrains ordinary people. Th is law was not, however, always self-
evident, and it was never self- executing. To some modest extent, these short-
comings could be dealt with by the Catholic Church. It possessed highly
learned men who could expound the content of the law, and it had various
spiritual weapons that it could wield against evildoers in high places. Medi-
eval Eu rope accordingly had extensive experience in the defi ning and en-
forcing of universal standards against governments.
What medieval Eu rope did not have was a conception of international
law in our modern sense, as a law applying specifi cally to relations between