How can karma exist in a free will universe? Several shamanic teachers have said that karma is only a teaching and that we can break bonds of association using intentional revocations.

It is quite true that karma is a teaching. It is a great teacher. It is the ultimate teacher because it is always ongoing, always working, always doing what it is designed to do—to give lessons to everyone. And no one can escape it. So it is the most thorough, the most powerful, and the most comprehensive teacher in existence because the entire universe is the classroom and it reaches every pupil. But it is not true that one can simply dictate to karma, alter it at will or on command. It is true karma can be healed with respect to an individual’s obligations and karmic debt accumulated through one's actions to create an imbalance in something. This is what triggers karma to begin interacting and to eventually visit each and every human being in proportion to their actions, whether good or for ill. The good deeds and acts of loving kindness will be rewarded because they will return to the person much as a mirror returns their reflection. If they are smiling, if they are loving, if they are reaching out and helping others less fortunate, if they are giving encouragement and upliftment, giving of themselves, helping the young, raising young of their own, being a loving spouse, a true friend, a loyal companion, a stalwart compatriot in an enterprise or an undertaking for the betterment of others—all such activities go in a kind of plus column with respect to putting love into the world and thereby the universe. These acts will be rewarded with further gains, further improvements, personal rewards and benefits as well, that will be amplified because the helping of another not only uplifts the self in the moment, by exercising the flow of love and encouraging greater love to come in to refill the quota, it also will come back to the originator amplified by the benefits to all who are touched by the act of loving kindness. The same, unfortunately, for all too many, is true of the negative actions that are undertaken through ignorance, through unawareness, through a deliberate choice to cause harm because of ill will, a desire for revenge, the consequence of inner bitterness and resentment that is targeted towards someone in particular, or what happens in a general dislike of a difference among individuals through organizations, membership in societies, political activities, and then other levels of interplay where people judge one another based on perceived neglect, disregard, or unfair treatment, and if there are labels associated become sources of bias and eventually prejudice if reinforced, and those dark perspectives will have a karmic consequence as they are enacted in the world. This comes back as a quite painful consequence, and it, too, is amplified in proportion to all of the secondary, tertiary, quaternary consequences as they spread outward from each victim of someone's disregard of this principle—that love should be in the driver’s seat and should be the motivation for all actions. And if that were so, the universe and particularly the local environment of your world, would change instantly. This cannot happen through simple choice and a decision by the person to simply disavow any responsibility to one's karma, and decree that it be ended. This only happens through a change of heart, a change within, an awareness of one's wrongdoing, and a kind of reckoning along with an energetic reassignment within all that is on record that has transpired. Unless that energetic signature is healed, it will be the reference point of what happens to the person. You cannot decree this out of existence. You cannot alter it with your thoughts alone. There must be a true interplay with what has happened in your world at your doing, and a reworking of the intention and the interaction that set things in motion in such a way as to recall the energies by repurposing them with an overlay that is, in effect, a kind of antidote, a healing intention that will change the energies on file. That is a healing, and healing does not happen by decree. It is a process and an interplay to bring in wisdom backed by loving energy to right the wrongs of the past. So these would‑be teachers are simply partly right and partly wrong.