The more correct answer as to if MJ is legal is "it depends."


Per Federal law:
No possession, use, growing, sale, for any reason other than sanctioned research.

Per state law:
Possession under an ounce is legal for everyone over 21.
Use by anyone over 21 is fine.
Purchasing is not legal unless you have a MMJ card.
Sale to MMJ card holders is fine.
While tolerated in some areas, MMJ stores are walking a thin line. Some have been raided by local PD, or threatened through their landlords by Federal alphabet agencies and closed that way.
Growing for MMJ card holders is fine, up to a certain amount of finished product, and a number of plants.

Again, the answer is, it depends.