GOVERNMENTAL SERVICES 137 
National authority is specified in the Constitu- 
tion, and so far as concerns veterinarians it is 
practically limited to the control of interstate and 
foreign commerce. The authority of the city is 
only such as has been given it by the state, and 
the city official has no authority outside of the 
city limits. The state has supreme police power 
over all matters within its boundaries, according 
to the ordinary interpretation of the Constitu- 
tion. 
100. Authority Determined by Legislation. 
Except possibly in the case of a very few of the 
principal officers, the duties and authority of all 
governmental representatives are determined by 
enactment. The enactment may be a constitution, 
a state legislative act, or a city ordinance. In 
each case the act is found in print or engrossed, 
and its provisions can be ascertained. The officer 
or employee should therefore become familiar 
with the exact wording of all enactments pertain- 
ing to his position. An act duly passed will be 
presumed to be law until it has been declared not 
valid. But the law may have been so declared, 
and still be permitted to remain upon the statute 
books. It therefore becomes necessary to know 
what judicial determinations there may have 
been upon the matter. 
101. Invalid Act Is No Defense for Officer. 
Where an officer of state or city has acted in per- 
fect good faith, relying upon a certain statute or 
ordinance for his authority, and in the course of 
his efforts he has worked injury to some citizen, 
either in person or property, if it shall later ap- 
pear that the statute was unconstitutional, or that 
