A Wizard's Pact is an agreement that your units will NOT come within two squares of their cities. If you're moving your units within two squares, you're violating the agreement.
A better question would be why do computer player units ignore WPs. They freely trespass and don't seem to observe the Pact at all.
A better question would be why do computer player units ignore WPs. They freely trespass and don't seem to observe the Pact at all.