That would depend on the laws of the state or country the offence was committed in. For a better answer ask the question again stating the state or country in the question.
In some jurisdictions it is a felony offense to assault an officer in the performance of their duties. The penalty will vary according to the wording of the laws of the various states.
It will depend on department policy, but some departments may not consider you if you have ever smoked marijuana. Consider that having smoked marijuana, you have broken several state and federal...