The Canadian PM, too, has given the green light for Canadian forces to shoot upon Libyan forces violating the no-fly zone.
Is this an act of war? Basically.
It's being conducted under a U.N. resolution. Canada (among other nations) has a
dark history of what can go wrong under U.N. resolutions.
Sure this can be seen as an aggression against a sovereign state, but the worst-case scenario is far worse. There is no indication that Gadhafi will respond to anything but force right now. It's at least in the best interests of vulnerable civilians for these international forces to be prepared to at least enforce the no-fly zone.
Of course, the no-fly zone business is likely the tip of a very big iceberg.