The law of trusts came from a combination of judge-made law and statutes. This area of law is old - it dates from about 1300 in Britain.
Trust law is older than the law of wills. Trusts allowed to pass land in landowner's discretion.
Because modern wills started about 1540 due to the passage of a British law allowing for wills to control real estate (rather than just non real estate until the statute was passed). Until that new Statute of Wills, trust law had been the method to avoid the British law that dictated whom would receive your real estate holdings.
Used to lower taxes on a death
Using trusts could also lower taxes. Under the British feudal system, on the death of the farmer taxes had to be paid to the lord above them. And those taxes (in part) passed on to the lord above them, until the King got the money that remained. Trusts were then called 'Uses' and the King did not like the fact that a majority of landowners were using Uses by 1500.
In sum, there were many lords (to be paid off) and ultimately some money made its way into the hands of the King.
Lawyers had devised this trust method: to put the land's ownership into the hands of several of the landowner's friends before he died, so upon the landowner's death, no death of the 'owner' took place. And so no taxes were due. Cute!
The law allowed the trust concept, without formal statutes on the subject. This was until the 1540 Statute of Uses tried to outlaw trusts as the King hated their effect of lowering estate taxes. The Statute failed to achieve its goal of eliminating trusts.
As trusts continued, judges in England would listen to a trust's beneficiary complaint if a trustee (i.e. the so-called 'friends') violated a term of a trust.
On the most basic level, it's this beneficiary's right to have his complaint dealt with by the court system - alleging a wrongful act of a trustee - that makes the trust a continuing, meaningful legal concept.
More recently, each state in the U.S. enacted its own laws regarding trusts.
Despite the passage of very limited trust statutes, trust law continues to be seen as a set of rules largely determined by judges' concepts of fairness.
Many authorities in the field, such as Charles Rounds editor of the 1898 treatise Loring and Rounds: A Trustee's Handbook, applauds the continuing role of judge made law in this field of law.
Massachusetts Trust Law
Since 2000, Massachusetts has passed statutes regarding trusts and called the Massachusetts Uniform Trust Code.
Despite this law's title, this statute provides for only a small aspect of Massachusetts trust law. Massachusetts has a long history of judge decided law on the topic and unless contradicted by the Massachusetts Uniform Trust Code, the previous trust law of MA continues to be in force.