I should have quoted a couple of sources regarding fuel tank venting.
For the US, here's the FAR, in part, that deals with it. Note that
(a)(1) deals with the icing problem of vents, hence Cessna's locating
it behind the strut, and (a)(4) deals with interconnected tanks such as
the 172/182's, so a vent system common to both tanks is required to
keep tank pressures equal.

23.975 Fuel tank vents and carburetor vapor vents.
(a) Each fuel tank must be vented from the top part of the expansion
space. In addition -
(1) Each vent outlet must be located and constructed in a manner
that minimizes the possibility of its being obstructed by ice or other
foreign matter;
(2) Each vent must be constructed to prevent siphoning of fuel
during normal operation;
(3) The venting capacity must allow the rapid relief of excessive
differences of pressure between the interior and exterior of the tank;
(4) Airspaces of tanks with interconnected outlets must be
interconnected;
(5) There may be no point in any vent line where moisture can
accumulate with the airplane in either the ground or level flight
attitudes, unless drainage is provided. Any drain valve installed must
be accessible for drainage;
(6) No vent may terminate at a point where the discharge of fuel
from the vent outlet will constitute a fire hazard or from which fumes
may enter personnel compartments; and
(7) Vents must be arranged to prevent the loss of fuel, except
fuel discharged because of thermal expansion, when the airplane is
parked in any direction on a ramp having a one percent slope.
snip

Canadians can find exactly the same thing in CAR 523.975.

Dan