Primary laws of archaeology
The Primary laws of archaeology consist of Stratigraphy (which includes the principle of original horizontality, and the principle of lateral continuity) and the Law of association.
Stratigraphy
If choosing between two interpretations, one given by the Law of Association and one given by stratigraphy, the archaeologist should always place the greater reliance on the interpretation developed by the stratigraphy, given that the stratigraphy can be shown to have strong integrity (without disturbance). This can by difficult because it is impossible to be certain that the stratigraphy has not been disturbed. Neither can the archaeologist be certain that something was not added to the assemblage he/she is trying to associate at a later date. The signs of disturbance, however, can be read more finely by a trained archaeologist for stratigraphy than for a collection, and therefore more original data can be gathered.
Law of Association
The Law of Association is only a method for creating a hypothesis about the meaning of an assemblage. It can be a plausible hypothesis, but there it ends. Stratigraphy is a testable method for interpreting the plausible hypothesis created by using the Law of Association. In such, the Law of Association is best used when one has the stratigraphy to test any developed hypothesis against. Without that stratigraphy, the association can answer no questions, due to its speculative and untestable nature. Yes, if you only have the assemblage itself taken out of context, then there are data one can extrapolate by using the Law of Association. This is basically what J A A Worsaae did to test the Three-age system. The data he gathered was qualitative in nature, but it solidified a basic concept in archaeology, which is that artifacts in an assemblage do have a relationship to each other. But he did not use the Law of Association alone to test the three-age system. He also used the idea of seriation, that similar objects in multiple collections can be regarded as actually similar in function or technological creation.