Question for Federal Law Enforcement Officers?

Hi, First I would like to point out that the question sounds incriminating and I'm sorry for that because I have never and do not have any feature plans of trying the substance I'm questioning about. (I'm morally against it). Anyway, I want to get into Federal Level Law Enforcement when I get older, but one of my second cousins told me something that I found interesting. He said he wanted to do the same thing as me but was rejected because he smoked weed in his teens. Is this true? will federal agencies such as the FBI, CIA, and DEA really reject you if you answer yes to that question on the lie detector? Or is it just if you have a criminal record of some sort including possession on weed or something similar? Thanks