One drug in particular that my husband takes daily is clonazepam. Here in USA it is a controlled substance with maximum 30 day supply at any time. Will this be a problem, to have this drug with us in Europe?
It is normally not a problem to carry any prescribed medicine through customs into European countries. Have a copy of the prescription, or other documentation, in case somebody asks. However since customs is a random stop only (95%+ are not stopped), and they ignore prescription meds, there will be no problem.
A bigger problem would be if you require extra supplies. You would need a prescription from a local doctor.