There seems to be many who are confused about the above question. Most of their bewilderment arises from a misunderstanding about what it means to be Catholic, what our Catholic freedom consists, and what teachings are considered definitive and which ones are merely matters of discipline and practice which are alterable.
To become a Catholic, one must first study the Catholic Faith, including all of the major definitive teachings, profess agreement with those teachings, and then, having assented to the teachings, receive the Sacrament of Confirmation. This Sacrament of Confirmation binds us to hold these Truths with the rest of the Catholic Faithful even to the point of martyrdom should that be required.
Therefore, to break with the Church and the rest of the Catholic Faithful, is in a manner of speaking, a renunciation of the Sacrament in which we solemnly avowed our assent. To do so is much more serious than just the character flaw or lack of integrity we have exhibited: indeed, it is a willful resignation from the Mystical Body of Believers that we supposedly joined.
Suppose, for example, that an immigrant to the United States became a citizen of our great country but refused to pay taxes or to serve in the military during the time of war. We would be outraged by such a person and agree that he never should have received his citizenship since he fully understood what responsibilities his citizenship required. However, in this situation, the new citizen (though having no right to break the law) would have the right to try to implement changes that he finds more suitable. Even the Constitution itself could be voted on and changed, as it is a man-made document which is within our rights to oppose or change though amendments are extremely difficult to revoke or alter.
The Church, however, is not the same type of institution. It is not a democracy where men decide what things should be held and what things should not be held. Because the Catholic Faith is a Revealed Faith, revealed by God, Who can neither deceive nor be deceived, Her definitive teachings on faith and morals must be fully and completely upheld and defended. It can never be voted on or ratified but simply accepted or rejected by His human creations.
So in matters of Faith or Morals we either accept them, whole and entire, or we reject them. If we hold these truths we are in communion with the Church and if not, our communion with the Mystical Body,which is Christ
We may object in matters of discipline and practice as they are not the dogma of the Church but we must remain obedient to them until such time that the practice is either changed or abrogated. It is not an act of disobedience to reject or criticize a practice that our conscience urges us to disapprove.
For instance, if I find that reception in the hand is a practice that makes the Real Presence of our Lord less recognizable and is thus creating a situation where people are losing their faith in this Definitive Teaching of the Church, I have every right to oppose it. I must honor the right of the Church to allow it, but I do not have to accept the practice as being either wise or what one would deem prudent.
So the answer to the headline: are Catholics free to dissent is dependent upon what manner of law we are speaking about. If the teaching is doctrinal, the answer is no. If it concerns practical or discipline related rules, the answer is yes with a caveat: we are obligated to be obedient to the instructions until such time as the rule is abrogated or changed.