Both terms are at different levels.
Previously, you should remark that any discipline has 3 axis: science, technique, art (Mario Bunge).
A theory is a type of knowledge: it is ideal, and could or not be related to facts (the Big Bang is a theory, although we cannot prove it; quantum mechanics is another theory that has been proven). It can or cannot be scientific, according to the method of knowledge development (science is created using the scientific method). But it is static knowledge, not necessarily related to other knowledge.
A law is not related to knowledge, but to causality: laws are relations between facts. Scientific laws describe the causal relationship between facts (e.g. the laws of thermodynamics describe the relationships between energy and mass; the second law says that if there's energy inside a thing, it tends to spread across the thing, you see? causality, if/then; action/reaction, etc.). Social laws determine the relationships between behaviors, in order to survive. For example, someone kills, then he must be isolated, so he stops killing and the group increases the probability of survival. Consider that causality is not a physical fact, but mental.
Quantum mechanics is usually not expressed as laws, since we don't understand them quite well. We have a theory that describes the facts perfectly, but we don't understand them (how can the past be changed? what does it mean? how can a thing have two states (which reduces to what is a thing?)? how can information be transferred faster than the speed of light?). Since causality is a mental feature, we cannot formulate causal relationships between facts we don't understand.