National and multinational companies do not respect state's laws.
Regarding testing, there are two HUGE factors which effect passing/failing a piss-test. I bought 30 tests to learn about my body several years back, when I was changing careers from carpentry (Smoking cannabis every day) to logistics (Random drug screenings, sometimes two in a week, sometimes one a year, with everything in between).
The two factors are: Metabolism and bladder-content.
Metabolism: Anecdotal evidence first: I had a friend - skinny as hell, could not put on weight - who smoked with me on a saturday and passed a drug test he did not know he was having on monday. Yes, he was inhaling. I did, however, tell him to fill the cup with piss from mid-stream. this applies to the bladder-content factor.
Okay, I used 20 tests on myself and 10 on my girlfriend. I do not have the exact results, but the conclusion was that I could pass a test after 2 weeks if I took urine from mid-stream, as THC metabolites tend to either float to the top of your bladder-contents, or sink to the bottom. If I took a sample from the beginning of the stream, It took about 40 days to piss clean. My girlfriend showed similar results, but she has a very slow metabolism. it took her 1 month to pass a test with a sample from mid-stream, and 2 months to pass a test from beginning-stream.
tl/dr chug water like a madman and fill the cup with urine from the middle of your stream, not the start and not the end.