The key question was would Saddam regime comply with the cease fire agreements? The purpose of the cease fire agreement was to end the war with Iraq.
{By invading Kuwait, Iraq gave the US, and any other country the international legal right to engage in warfare with Iraq. Members of the international communty *could have* decided not to engage in warfare, they could have expressed their protest, but over time accepted to fact the Kuwait as a sovereign state was replaced by Iraq. But because of US leadership [strongly affected by UK's prime minister] we led a coalition to use force against Iraq in order to remove Iraq from Kuwait.}
Preemption is NOT an attempt to replace international law, rather it's an internal American policy regarding how the US responds to international problems involving US security {which needs be understood in the context of what *was* and *is* US policy}. The US govt is not going to violate international law- rather enforcing and strengthening international law is seen as the way to a more peaceful world. Preemption is about what do you do with countries which are violating international law- what you do with countries which are hostile to the US- which [because of the connectiveness of the world] extends to formal/legal US allies and less aligned countries who are supportive of maintaining international peace.

With all the above said, the key to whether the US attacked Iraq was depending mostly on the leadership of Saddam. If Saddam had complied with cease fire agreement, we won't have needed to go to step two: How do we get Iraq to comply with the cease fire agreement? At step two, such things as preemption, intelligence, and presidental leaderships are factors. Returning to step one, intelligence questions can be: Is Saddam actually cooperating with UN inspectors in order rid his country of any WMD programs? If Saddam is acting a certain way, why is he acting this way? Are problems the UN inspectors are facing due to their incompetence in understanding and dealing with the Iraqi regime? Etc.